Moldings Glossary
Base, casing, crown and every profile term in between. If it's a trim piece and a name for it, this is where it lives.
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Jump to a term: Apron / Stool (vs. Sill) Attic Access (Cover) Back Band Backing / Blocking Base Cap Base Shoe Baseboard Bullnose (Profile) Casing Chair Rail / Picture Rail Colonial / Clamshell / Craftsman (Flat) Profile Corner Block Cove (Molding) Crown Molding / Spring Angle / Bed Mold Crown Splice Field (Panel) Head Casing Jamb Extension Mullion Strip Picture-Framing Plinth Block Quarter Round Return / Self-Return Rosette Scarf Location / Scarf Joint Shiplap / Nickel Gap / Starter Course Speed Base Stool Horn Wainscot / Board-and-Batten Window Seat / Window Sill
Apron / Stool (vs. Sill)
Also called: window apron.
On a stool-and-apron window, the stool is the protruding horizontal shelf at the bottom (functionally the interior sill); the apron is the flat trim piece nailed beneath it.
Not the same as a sill. The sill is the exterior-facing sloped part that sheds water. The stool is the interior trim piece, and it is what people actually mean when they casually say 'window sill' indoors.
Attic Access (Cover)
Also called: scuttle, scuttle lid, scuttle hole cover.
A framed cover panel that seals an attic access opening while allowing it to be opened.
Back Band
Also called: backband.
A separate strip of molding applied to the outer edge of flat casing to add a shadow line or thicker look.
Backing / Blocking
Solid wood (or engineered) framing added behind drywall to give fasteners something solid to bite into, at railing points, cleats, etc.
Base Cap
A small decorative molding applied to the top edge of flat baseboard stock.
Base Shoe
Also called: shoe molding, shoe mold. Shop talk: shoe.
A thin, narrow strip of molding installed at the bottom edge of the baseboard, right where it meets the floor. Flexes to follow small dips the baseboard cannot.
Pro note: Not the same trim as quarter round, even though they cover the same job. True quarter round is a perfect quarter-circle, equal height and depth. Base shoe is a quarter-oval instead, taller than it is deep.
Do not confuse this with a baluster shoe, the small metal cap where a stair baluster meets the tread. Both are called 'shoe' on site, but they are different parts.
Baseboard
Also called: base, base molding, base trim, mopboard, mop board, skirting board, floor molding, base board.
The trim that runs along the bottom of a wall where it meets the floor, covering the joint and protecting the wall from scuffs.
Pro note: Hold-up height varies by flooring type (3/8-1/2in over carpet/LVP, tight to wood floor, 3/4in on main-level tile). Glue every miter. Inside corners get coped, not mitered.
Bullnose (Profile)
A rounded-edge profile applied to shelf edges, stair nosing and drywall corners, a cross-cluster term.
Casing
Also called: door casing, window casing, architrave, trim.
The flat trim that frames a door or window opening, covering the gap between the jamb and the drywall. Mitered casing meets at 45-degree corners; butted casing meets square.
Pro note: Set off the jamb reveal, not leveled piece by piece. Reveal is 3/16in, a single value, everywhere. Glue every miter.
'Trim' is broader than casing (covers all finish woodwork); do not treat as a strict synonym.
Chair Rail / Picture Rail
Chair rail = horizontal trim at chair-back height; picture rail = trim near the ceiling for hanging picture wires.
Colonial / Clamshell / Craftsman (Flat) Profile
Named casing and base profile shapes. Colonial and Craftsman are the two names used on a materials list; clamshell is another name for the flat Craftsman-style profile.
Corner Block
A block used at a casing corner instead of mitering, a near-relative of Rosette.
Cove (Molding)
Also called: coving.
A concave-profile molding; also used generically for the shape at ceiling/soffit transitions.
Crown Molding / Spring Angle / Bed Mold
Also called: crown moulding, cornice.
Crown runs the wall-ceiling joint at an angle (its spring angle), typically cut with compound miters; bed mold is a small crown-adjacent transition molding.
Cove and crown are not interchangeable: cove has a simple concave profile; crown reads more ornate with a compound sprung profile. Bed molding points into the corner (supporting profile); crown points out (terminating profile).
Crown Splice
Field application of a scarf joint specifically to crown molding.
Field (Panel)
The flat central panel area on a raised-panel door or wainscot panel, as opposed to the surrounding stile/rail frame.
Do not confuse this with field as a layout term, covered on the Layout and Shop Talk hub, the open expanse of floor or wall away from a border. Here it means the flat center panel of a raised-panel door or wainscot.
Head Casing
The top piece of a casing set, distinct from the side casing legs.
Jamb Extension
A strip of wood added to a jamb edge to bring it flush with a wall that is thicker than the jamb.
Mullion Strip
Also called: mull, mull post, mullion casing, mull strip.
The vertical or horizontal member that joins two separate window or door units into one combined opening.
Pro note: Mullion is structural/joining, dividing SPACES. Do not confuse with Muntin, which divides GLASS.
Picture-Framing
The standard four-mitered-corner casing method for a window, as opposed to stool-and-apron.
Plinth Block
Also called: plinth, base block.
A decorative block at the base of a door casing that the side casing lands on, wider than the casing itself.
Quarter Round
A molding profile that is a true quarter-circle in cross-section, equal height and depth. Not the same as base shoe (a quarter-oval).
Pro note: This is a genuine, sourced correction to a common conflation; lead the entry with it.
Return / Self-Return
A return is the small mitered piece that turns a piece of molding, usually a handrail, back to the wall so end grain does not show. A self-return is cut from the same stock as an integral extension instead of a separate glued-on piece.
Rosette
A decorative corner block, usually carved with a flower-like pattern, set at the upper corners of casing so the side legs and head casing all land with square cuts instead of a mitered corner. It does at the top of an opening what a plinth block does at the bottom.
Scarf Location / Scarf Joint
A scarf joint splices two lengths of molding with overlapping mitered cuts, always located over a stud for nailing support.
Pro note: "Tight scarf joint, no caulk" is part of the baseboard money shot.
Shiplap / Nickel Gap / Starter Course
Shiplap is overlapping-rabbet board siding/paneling; nickel gap is a shiplap variant with a small (nickel-coin-width) reveal between boards.
Speed Base
Shop talk: speed base.
A one-piece baseboard profile shaped to look like a flat board topped with a small bed-mold cap, installed with simple angled corners instead of coped joints.
Stool Horn
See Horns (Doors hub) - the stool ends that project past the side casing.
Wainscot / Board-and-Batten
Also called: batten board.
Wainscot is a lower-wall wood treatment (paneling, beadboard, or board-and-batten) running to a chair-rail-height cap; board-and-batten is one style using vertical boards over battens.
Window Seat / Window Sill
A named PieceWrk service with its own guide, a built interior seat or sill treatment at a window.
What does your crew call it? If you use a different word for something on this page, or we are missing a term you use every day, tell us and we will add it.