mortise

A mortise is a cavity cut into a piece of wood, metal, or stone to receive a corresponding projection called a tenon. In woodworking, the mortise-and-tenon joint uses a mortise to receive a tenon from another piece, forming a strong, resistant joint. Mortises can be through mortises, which pass completely through the workpiece, or blind mortises, which terminate before the far face.

Proper sizing and alignment are essential. The mortise width equals the tenon thickness, and the depth is chosen so the tenon shoulders seat cleanly. Typical practice aims for a snug fit with minimal extra clearance; glue, pins, or wedges may be used to secure the joint. In timber framing and heavy joinery, longer and wider mortises provide greater strength.

Common tools and methods include mortising chisels, hand or powered mortisers, brace-and-bit mortising, and routers with templates. Layout is critical to ensure the tenon aligns with mating members; waste wood is removed in stages to keep square walls.

In addition to furniture and timber framing, mortises are used in door construction for mortise locks, where the lock mechanism is housed in a recessed cavity in the door edge or face. A properly formed mortise ensures operation and durability of the hardware.

The term mortise derives from Old French mortaise, meaning a “pocket” or “hole.”