On this page
Introduction #
Door and window parts get mixed up on a jobsite more than any other vocabulary in the trade: a door stop against a door bumper, a sill against a threshold, a mullion against a mull strip. The Window and Door Manufacturers Association is the trade body behind the standards.
A door or window opening is built from dozens of small named parts, and a few pairs get confused on a jobsite over and over: a door stop and a door bump are not the same thing, and a margin is not a reveal. This guide names every part of a door and window opening, in order from the rough framing out to the casing, so you know exactly what you are holding and what to call it when you order it or talk about it with the crew.
This is not an install guide. Most parts below link to the guide that actually covers hanging it, casing it, or trimming it out; a few, like the rough framing members and the window sash, sit outside what this crew installs and get no guide link. What you get here is the vocabulary: what each part is, where it sits, and what it is not, because a wrong name on a supply order or a text to the lead costs more time than a slow measurement ever does.
A few of these terms already get a full treatment elsewhere in this series. A separate guide in this series covers the 3/16 inch reveal in depth, another covers what a door skin is and where MDF and HDF actually show up on a door, and species selection has its own guide too. This guide points at each one instead of repeating it, and adds only what is specific to doors and windows.
Before You Begin #
Prerequisites #
You do not need any tools on hand to read this guide. If you want to check a claim against real material, grab a scrap door jamb, a piece of door stop, and a window casing offcut off the truck. Holding the actual parts while you read fixes the names faster than the page alone.
What You Need To Know #
Most of the confusion in this list comes from two words doing two jobs. "Stop" means a strip of molding on a jamb in one context and a piece of hardware on a wall or hinge in another. On this crew's jobs "riser" means a piece of finish trim inside the house and a structural board on an exterior step, the same kind of split, though risers stay out of scope for this guide entirely. Keep every pair of look-alike terms below apart in your head. Even this crew's own notes have used stop and bump for the same hardware, so do not count on habit alone.
Every part in this guide belongs to one of four places, and knowing which one tells you which install guide actually covers it.
- Rough opening. What the framers build: jack studs, king studs, header, and the rough sill.
- Jamb and frame. What the door or window unit itself sits in, once it is set.
- Door or window unit. The slab or the sash, and everything built into it.
- Casing and trim. What covers the gap between the jamb and the finished wall.
Door Jamb Types: Flat, Rabbeted, and Split #
A door jamb comes in three constructions, not four. Calling a fourth type "adjustable" describes the same product as a split jamb, not a separate one; drop the fourth name.
A standard flat jamb is a plain, flat board on all three sides of the opening, with no rabbet or built-in stop cut into it (it still gets hinge and strike mortises like any jamb). One specialty type, a kerfed flat jamb, has a slot cut into its edge so drywall can wrap in with no casing. Nothing on a flat jamb stops the door on its own, so a separate strip, the door stop, gets applied to the face after the jamb is set. A rabbeted jamb has that stop built in: a step, called a rabbet, is cut into the jamb itself, and the door closes against that step instead of against a separate applied piece. A split jamb is two thinner halves that telescope together from opposite sides of the wall, adjusting to whatever the actual wall thickness turns out to be. It often ships with the casing already attached to each half, which is why it shows up so often on factory pre-hung interior doors.
A factory pre-hung door arrives with its jamb already made, commonly finger-jointed pine or MDF. When this crew builds a jamb itself, for a cased opening with no door or for an interior window frame, it is 1x stock, MDF, pine, or poplar per the crew's own frame guides, ripped on the table saw to match the wall thickness measured on the actual opening, not a catalog number. Jamb width tracks the wall it sits in: 4-9/16 inches covers a 2x4 wall with 1/2 inch drywall on each side, and 6-9/16 covers a 2x6 wall, which is why exterior doors more often arrive with the wider jamb (one published guide names both sizes for an exterior jamb). Measure the actual wall before you rip jamb stock to width.
Do not confuse a split jamb with a split stud. A split stud is framing: one of the thin studs that build the two stud walls a pocket door slides between, all built into the wall before drywall. A split jamb is finish trim, a two-piece jamb, and this crew's guides use the name for two parts: on a swinging pre-hung door the halves telescope together to fit the wall thickness, and on a pocket door it is the two-piece finish jamb that goes in after drywall and lets the slab slide through. On a pocket door the two words name two stages of one job, split studs at framing and split jambs after drywall.
Plan view, wall to the left of each jamb. Not drawn to a fixed scale.
Jamb Extensions and Door Stop #
A jamb extension bridges the gap between a jamb that does not reach the finished wall and the wall itself, so the casing has a flat, even surface to land on. On a door, that usually means individual strips glued and nailed onto the existing jamb edge. On a window, it is more often a full four-sided box built to the exact depth of the wall and set into the rough opening before the window's own trim goes on. Both are their own job with their own guide; see How to Install a Door Jamb Extension and How to Install a Window Jamb Extension. One published guide warns that bare MDF or raw wood left exposed behind the casing can pull in moisture and swell later, creating a bump that telegraphs right through the casing; sealing that edge before paint is the painter's step, not ours.
Two different things get called a "stop" on this crew's jobs, and they are not the same part. A door bump is hardware: a wall, baseboard, or hinge-pin stop that keeps a swinging door from hitting something else. A door stop, the term this section means, is the strip of molding applied to the face of the jamb that the door closes against. Keep the two words apart the same way this crew keeps two different meanings of "riser" apart elsewhere.
Which jamb type you have decides how the stop gets applied. On a flat jamb, the stop is a separate strip, and that strip is what "door stop" usually means. Most pre-hung doors arrive with it already applied at the factory; this crew nails one on only when it builds a jamb itself, like an interior window frame or a cased opening with no door. On a rabbeted jamb, the stop is cut into the jamb itself, so there is no separate strip to apply at all. One published guide's own material list gives a stock size for this strip: "standard door stop 7/16 by 1-3/8 inch." Treat that as what that guide runs, not a confirmed company-wide spec, since no house rule fixes a single dimension for door stop stock. That same guide miters the stop's corners at 45 degrees and installs it on one side of the frame first, before the glass is set, then closes it out with a matching strip on the second side (that guide covers a fixed interior window frame, not a swinging door).
Door Sill vs Threshold, and the IRC Landing Numbers #
A sill and a threshold are not the same part, even though people use the words interchangeably on site. A sill is the horizontal member at the bottom of the opening, whether that is the rough sill framed under a window or the sloped, weather-shedding piece at the bottom of an exterior door unit. A threshold is the strip that sits under the door itself, adjustable on most exterior units, that the door bottom presses down against when the door is closed. A pre-hung exterior door unit typically ships with its threshold already attached.
Code sets numbers on how a landing relates to that threshold. Under IRC section R311.3, an exterior door needs a landing or floor on each side, at least 36 inches deep in the direction of travel and at least as wide as the door itself, with a narrow exception for a small balcony. At the required egress door, the landing cannot sit more than 1-1/2 inches below the top of the threshold, except that the outside landing may drop to 7-3/4 inches if the door does not swing out over it. Every other exterior door on a one- or two-family job gets the 7-3/4 inch allowance outright, and can skip the landing altogether if it opens onto a stair of two risers or fewer and does not swing over it. Apartment and multifamily work usually falls under a different code with its own entry rules, so do not carry these numbers over without checking. This session confirmed that text through the 2021 edition served on up.codes; it did not confirm which edition Omaha, Douglas County, or Sarpy County has actually adopted, so check the locally enforced edition before quoting these numbers on a specific job.
On a house-to-garage door, there is no exterior water to manage, but it is not only an air and heat job either: code treats this door as part of the fire separation between the garage and the house, covered under door core types below, which is why it gets self-closing hinges. For the gap between the jamb and the rough opening, this crew uses door-and-window-rated low-expansion foam, the process covered in full in How to Install a House-to-Garage Door. This crew does not run an exterior caulk bead to the siding on that door; the foam is the whole seal. A weather-exposed exterior door is a different job entirely, with its own sill pan and flashing steps, covered in Installing a Weather-Exposed Exterior Door: The Extra Steps.
Door Sweep, Astragal, and T-Astragal #
A sweep is the strip mounted along the bottom edge of a door that closes the gap between the door and the floor or threshold. On an interior slab, like an apartment entry door, it mainly cuts sound and drafts between the unit and the hallway. On a weather-exposed exterior door it works with the threshold to keep rain and snow out. A house-to-garage door sits in between: built like an exterior door, but with no weather on the garage side, its sweep is doing the same draft job as an interior slab. A sweep gets fit to the actual slab it is going on, not ordered as one fixed length for every door; see How to Install an Apartment Entry Slab Door with a Sweep for the fitting steps.
An astragal, and its T-astragal variant, are moldings at the meeting point of a pair of doors, most often a French or center-opening pair. On this crew's jobs, one door in the pair is active, the one used every day, and the other is inactive, secured shut with flush bolts and opened only when the full width of the opening is needed, moving furniture and similar. The T-astragal, also called the meeting strip, attaches to the edge of the inactive door. It gets its name from its shape in section: a T whose stem fills the gap between the two doors and whose flat top laps across the face, where a plain astragal is a flat or molded strip applied to one door with no stem. It gives the active door's latch something to catch when the pair closes, so the inactive door has to be secured first or the active door will not close right. Many pre-hung French door units ship with the flush bolt pockets already cut, and once both bolts engage, the inactive door should feel completely solid; any play there and the astragal will move enough that the active door's latch stops catching. See How to Install an Interior Center-Opening or French Door for the full sequence.
Mullion, Mullion Strip, Transom, Sidelight, and Mull Strip #
A mullion is the structural or frame member between two window units set side by side. A mullion strip, sometimes shortened to mull strip on a supply order, is the trim piece that covers the gap between those two units on the finished side, the same job casing does around a single window. The two words name different things: one is framing or frame, the other is the trim over it. The width of a mull strip, and whether it runs as one flat piece or a built-up profile, follows the approved casing style for the job rather than a fixed dimension. See How to Case Ganged Windows for how a mull strip ties a group of windows into one finished unit, for the strip between two units. The published guide titled How to Install a Mullion Strip is about a different part that shares the name: the applied strips that divide a single window's glass into a paneled look. Read the title, then read the first paragraph, before you reach for either one.
A transom is a fixed window set above a door opening, usually to bring extra light into the space. It is not a stand-alone frame the way an interior window is; it ties into the door casing below it and gets cased as one continuous run with the door, holding the same 3/16 inch reveal through both. See How to Install a Transom Window Above a Door.
A sidelite, also spelled sidelight, is a narrow fixed window set beside a door, often in pairs flanking an entry unit. A door with its sidelites reads as one combined unit once cased, the same way a transom over a door does.
Brick Mould #
Brick mould is the usual exterior trim that covers the gap between a door or window frame and the siding around it, doing outside the job that casing does inside; some units get a flat exterior casing in that spot instead. It often ships attached to the door or window unit already. A separate guide in this series covers brick mould's profile, and the drip cap that sheds water off the top of an exterior opening, in full.
On a house-to-garage door, brick mould gets pushed and held tight against the framing around the rough opening, the same way interior casing gets pulled tight to a jamb.
Pre-Hung vs Slab Doors #
A pre-hung door arrives as a complete unit, the slab already hung on its jamb with the hinges mortised in. A slab-only order is just the door panel, no frame, meant for an opening where a frame already exists, an existing jamb being reused or a frame another trade already set. On apartment and multifamily work, this crew's job is sometimes the slab only, with another trade setting the frame; whether a given job covers both the frame and the slab or just the slab depends on the general contractor, so confirm the scope before you order material.
Wood-cased interior pre-hung doors always go in after drywall is finished. Installing before drywall is welded hollow metal frame practice, covered later in this guide; a knock-down hollow metal frame goes in after drywall, the same timing as a wood-cased pre-hung door. In residential work, the only interior doors this crew sees going in before drywall are apartment unit entry doors, whose welded frame the framers or the door supplier already placed. See How to Install a Pre-Hung Door and How to Install an Apartment Entry Slab Door with a Sweep.
A pre-hung unit gets named by its hinge side, standing on the side the door swings toward you: hinges on your left makes it a left-hinge door. Some suppliers name the same door by "hand" instead, which inverts the naming, so confirm which convention a supplier used before you order. See door handing.
Setting a pre-hung jamb plumb takes a set number of shim points, in order, and the count changes with door height. A standard 6 foot 8 inch door has three hinges and takes 9 shim points, 4 on the hinge side and 5 on the strike side; an 8 foot door has four hinges and takes 11, 5 on the hinge side and 6 on the strike side. On both heights, the strike-side point nearest the latch sits just above the strike plate and never gets a nail into the latch area itself.
| Door height | Hinges | Hinge-side points | Strike-side points | Total |
|---|---|---|---|---|
| 6'8" | 3 | 4 | 5 | 9 |
| 8'0" | 4 | 5 | 6 | 11 |
See How to Install a 6'8" Solid Core Pre-Hung Interior Door and How to Install an 8'0" Solid Core Pre-Hung Interior Door for the numbered shim order on each height.
Hollow core doors get nailed on only. A solid core door gets that same nailing, plus one number 9 by 3 inch screw through the top hinge into the framing, replacing the short factory screw there; no other hinge gets one. In the solid core guide's own words, that one long screw at the top hinge is what keeps a 50 to 70 pound door from sagging and losing its latch.
The margin is a different gap from the reveal. Margin is the gap between the door slab itself and the jamb, at the head, hinge side, and strike side, and it is 1/8 inch. Reveal is the casing setback from the jamb edge, a separate number that a separate guide in this series covers in full. Keep the two words apart; margin is the slab-to-jamb gap, and reveal is never used for that gap.
Door Core Types: Hollow Core, Solid Core, Stave Core, MDF Molded Doors, and What a Door Skin Is #
A hollow core door is light: the solid core guide puts a standard 6'8" hollow core slab at about 25 to 35 pounds. Inside it is mostly air, a lightweight core inside a solid or engineered perimeter frame that forms the door's actual edge and stiles. The same guide puts a solid core door of that size at 50 to 70 pounds, sometimes more on a wider slab, because the space between the same two faces holds solid material instead of open air. The 6'8" solid core door guide linked above covers what that weight changes about the hang; this guide only names the parts.
A door skin is the thin, flat face panel, usually HDF and sometimes thin plywood, glued to both sides of a hollow-core door over its honeycomb core; in a factory-built door it is a part of the door, not something this crew orders on its own. A separate guide in this series covers door skins and what sits behind them.
Stave core construction is a third option: solid wood strips, often pine rather than a hardwood, glued up edge to edge inside the door, faced with a thin skin, often about 1/4 inch, giving a door that machines and holds hardware more like solid lumber than a honeycomb core does. A molded door, often called an MDF or molded-panel door, is a different build again: its raised or flat panel look comes from a face skin pressed into shape at the factory, over a hollow or solid core, instead of from separate stiles, rails, and panels glued into a frame. Both are real products from major door makers; which one shows up on a given job depends on what the plans specify. What sits behind a door's face skin is not always the same thing job to job either, MDF, particleboard, glued-up solid wood strips, or a mineral core on a fire-rated door; the skin is what makes the door look finished, the core underneath is what makes it heavy or light.
A house-to-garage door is not just any interior door. Under IRC section R302.5.1, the door between an attached garage and the house has to be solid wood at least 1-3/8 inches thick, a solid or honeycomb-core steel door of that same minimum thickness, or a 20-minute fire-rated door, and the code itself says it has to be self-latching and close on its own with a self-closing or automatic-closing device. This crew installs self-closing hinges on the top and bottom hinge only, on house-to-garage doors and nowhere else; the middle hinge stays a standard butt hinge. See How to Install Self-Closing Hinges.
Hollow Metal Frames: Knock-Down vs Welded #
A hollow metal frame is a steel door frame, common on apartment unit entries and commercial-style openings, and this crew installs two different products under that name. A welded frame arrives from the shop as one unit, head and jambs welded together, and it goes into the rough opening before drywall is hung, so the rock can butt into the frame's return. A knock-down frame ships as three loose pieces, a head and two jambs, that wrap around a finished wall instead, going in after drywall.
The two get anchored differently, too. A welded frame anchors to the studs through strap anchors on the back of the jambs, using a number 8 by 1 inch modified truss head stainless self-tapping screw. A knock-down frame fastens straight through its face with 2 inch coarse-thread drywall screws, and its slab hangs at the same time as the frame, since that is how the margins get set as the frame tightens up. Neither type gets shims, and neither ever goes into masonry; block, concrete, and grout sit outside the scope of both guides entirely.
A welded frame is frame only; its slab and hinges come on a later, separate trip. A knock-down frame hangs its slab at the same time, hinges included, since the slab is what sets the margins. The lockset and the closer are separate jobs on both. One knock-down frame guide notes its own manufacturer calls for a rough opening 5/8 inch taller than the frame's net length and 1 to 1-1/4 inch wider than its net width; check the actual kit's spec sheet rather than assuming a fixed clearance across brands. See How to Install a Knock-Down Hollow Metal Frame and How to Install a Welded Hollow Metal Frame.
Pocket Door Frame vs Pocket Door Jamb Kit: Two Separate Purchases #
A pocket door frame is the steel track and split-stud cavity built into the wall during framing, before drywall goes up. It is the skeleton the whole pocket door depends on. On this crew's jobs it is normally the framing crew's work, done by this crew only on special request; the rough opening width runs roughly twice the door's nominal width, plus the kit's own jamb allowance, per the frame kit's spec sheet rather than a fixed rule. See How to Install a Pocket Door Frame.
A pocket door jamb kit is a separate purchase, and it does not come included with the frame. Major hardware makers sell the two as different products: the frame kit carries the track and the split steel studs, and a jamb kit, ordered separately, supplies the split jambs and the strike jamb, ready to install once drywall is up. Not every job orders the jamb kit: this crew's own pocket door guide says the split jamb pieces may come with the frame kit or get made on site from stock. This crew's finish-stage work, the slab, the roller hardware, the split jambs, and the casing, all happen on that later trip, covered in How to Install a Pocket Door and How to Install Privacy Pocket Door Hardware. An 8 foot pocket door needs jamb stock long enough to reach the full height, factory length or spliced, and the 8'0" guide warns that a spliced jamb binds if it does not run true; see How to Install an 8'0" Pocket Door.
Bypass vs Bifold: Track and Pivot Hardware #
A bypass door slides side to side on an overhead track, two or more panels overlapping each other as they open; it suits wide openings, typically 4 feet and up, though a double bifold can cover that same width when the job wants full access instead of a sliding panel. A bifold door folds in half on a pivot instead of sliding past itself, and it is one of the most common closet door styles on a standard-width opening.
A bypass track gets cut to match the actual opening width, not some multiple of it. If a track ships too long, it gets trimmed with a hacksaw to fit; there is no rule that runs the track two or three times the opening. Stock track lengths from the major hardware makers are sized to common closet openings, 4, 5, and 6 feet and so on, built around that same idea rather than any multiplier. Bypass panels overlap 1 to 1-1/2 inches at the center when both are closed, per the bypass door guide, and a floor guide at the center of the opening keeps the bottom of each panel from swinging out or drifting sideways. A bifold track is sized the same way, cut to the opening width if the stock length runs long.
Bifold hardware pivots on a spring-loaded pin at the top and a pivot bracket at the bottom on the pivot side, mounted to the floor or to the jamb depending on the kit, with a roller guide pin at the top outer corner of the track-side panel riding in the overhead track. Bypass hardware has no pivot at all; each panel hangs from roller hangers that clip to its top edge and ride the track.
See How to Install Bifold Doors, How to Install Bypass Doors, and How to Finish a Bypass Door Install. Frame kits for both styles at 6'8" and 8'0" are their own guides: How to Install a 6'8" Bi-Fold or Bypass Door Frame and How to Install an 8'0" Bi-Fold or Bypass Door Frame.
Window Sill vs Stool, and the Apron #
On the interior side of a window, two parts sit at the bottom, the stool and the apron, and each is a separate piece. The stool is the flat, horizontal ledge that sits on top of the sill, the shelf-like piece a plant or a coffee cup actually rests on. Stool stock typically runs 1x6 or 1x8, sized to the window. Below the stool, an apron is a trim board that visually supports it and ties the bottom of the window into the rest of the casing; its ends usually line up with the outside edges of the casing above it.
A stool commonly extends past the casing on both sides, often by an inch or two, an extension called horns. Sill, in this same conversation, means something different again: it is either the sloped exterior part of the window unit itself, or the rough sill framed under the window opening, not the interior stool. See How to Install a Window Seat or Sill for the stool and sill install steps, which cover the sill and stool but not the apron, and How to Case a Window for the picture-frame method; neither guide currently walks through fitting the apron.
Picture-Frame Casing vs Stool-and-Apron Casing #
Interior windows get cased one of two ways, and the customer's spec decides which, not a default this crew picks on its own. Picture-frame casing runs mitered corners on all four sides, top, bottom, and both legs, the same joint pattern as a picture frame. Stool-and-apron casing skips the bottom miter: the stool and apron go on first, and the side casing legs land on top of the stool with a square cut instead of a mitered one.
The install order differs along with the joint. On a stool-and-apron job, the stool and apron go on before the side casing, so the legs have something to land on. On a picture-frame job, all four pieces are just casing, mitered together with no stool or apron involved at all. Four mitered corners is the most common style this crew runs and the one the core casing guide teaches, but it is not the only style a job can call for; where the approved style differs, that variant gets its own guide rather than a change to the core steps. See How to Case a Window, How to Case Tall Windows, and How to Case Ganged Windows for how the picture-frame method scales to different window heights and groupings.
Sash, Muntin, and Grille: True Divided Lite vs Simulated Divided Lite (SDL) and Grille-Between-Glass (GBG) #
The sash is the moving part of a window that actually holds the glass, the framed unit that slides or tilts inside the fixed window frame. Casing or an extension jamb should not crowd the sash or its hardware; check the clearance before you nail anything close to it.
A window can show divided panes of glass three different ways, and only one of them is real divided glass. True divided lite, TDL, construction uses individual panes of glass, each one its own separate piece, held apart by wood or vinyl dividers called muntins. Simulated divided lite, SDL, keeps each pane as one uncut sheet of glass, usually part of a sealed double-pane unit, with grille bars applied to its surface, to look like divided panes without the extra seams a true divided window has; those grille bars can sit on the exterior face, the interior face, or both, depending on the look a customer wants. Grille-between-glass, GBG, places the grid pattern between the two panes of a double-pane glass unit instead, so on its own nothing sits on either glass surface; some makers also sell a version that adds exterior grille bars over GBG for a deeper shadow line, so check what the window order specifies.
A muntin, in the strict sense, is the bar, usually wood or vinyl but sometimes matching another frame material, that actually separates individual panes on a true divided lite window; the word gets used loosely for SDL and GBG grille bars too, even though those bars are not separating anything physically.
Extension Jambs and Mull Kits on Windows #
A window jamb extension is a four-sided box, built to the depth of the wall and set into the rough opening so the window's own jamb reaches the finished wall surface. It is a different build from a door jamb extension, which is individual strips glued and nailed onto an existing door jamb edge rather than a stand-alone box. See How to Install a Window Jamb Extension for windows under 90 inches, and Window Jamb Extension for Medium-Tall Windows and Window Jamb Extension for Tall Windows (120 Inches and Above) for taller openings. Taller openings need more shim points as the height climbs, and past 120 inches typically a second person to hold the box steady while it gets shimmed from a ladder; see those two variant guides for the specifics.
An egress window, one sized and placed to serve as a legal emergency exit, still gets built as a jamb extension job on this crew's jobs, per the crew's own field notes; the extension build itself does not change because the window is rated for egress. The one exception is a higher-end window that ships with its own factory extension jambs already sized to the wall; there no box gets built, egress-rated or not.
A mull kit is the hardware and trim a manufacturer sells to join two window units into one structural assembly, usually on a flat surface before the assembly goes into the rough opening and sometimes in the opening itself when the combination is too heavy to lift joined, distinct from the field-built mullion strip covered earlier in this guide, which trims out two units that were already set as separate frames. Whether a given group of windows arrives pre-joined with a mull kit or gets ganged together on site with a field-built strip depends on what the window order specified; see How to Case Ganged Windows for the field-built version.
The framing below a window's rough sill carries its own short studs, called cripple studs, that run down to the bottom plate and help support the sill above them. The same word names the short studs that run up from a header to the top plate above a door or window. You will hear the word on a jobsite when a rough opening gets discussed, even though this crew's own work starts above that framing, at the jamb extension and the casing.
Door and Window Parts Quick Reference #
Ten look-alike parts, what each one actually is, and the part it is not.
| Part | Where it sits | Not to be confused with |
|---|---|---|
| Door stop | Applied to, or cut into, the jamb face, where the door closes against it | A door bump, which is hardware |
| Door bump | Wall, baseboard, or the hinge pin | The door stop molding on the jamb |
| Margin | The gap between the door slab and the jamb, 1/8 inch | The reveal, a casing measurement |
| Sill | The window unit's sloped base, or the rough sill in framing | The interior stool |
| Stool | The interior ledge that sits on top of the sill | The sill itself |
| Threshold | The strip under the door that the door bottom closes against | The sill |
| Astragal / T-astragal | The meeting strip between a pair of doors | A mullion |
| Mullion | The frame member between two window units | The mullion strip, which is trim |
| Mullion strip | Trim covering the gap between two window units | The structural mullion |
| Split jamb | A two-piece finish jamb that telescopes to the wall thickness | A split stud, which is framing |
