rabbet joint
See definition at rabbet.
rabbet joint: two boards locked by cut shoulders
A rabbet joint is formed by cutting a stepped shoulder, or rabbet, into the edge or end of one board, then sliding a second board into that recess so its face sits flush with the first. The rabbet itself is a rectangular notch cut partway through the wood; when two rabbeted pieces interlock, they create a joint stronger than a simple butt joint because the mating surfaces are supported on two planes rather than one.
The rabbet is typically cut with a saw, router, or specialized rabbet plane, removing wood to a depth of roughly one third the board thickness. A common setup has the rabbet running along the inside corner of a frame or box, with the second board's edge fitting snugly into it. The shoulder of the rabbet, the inner vertical face of the cut, bears the load; the horizontal bottom of the rabbet provides lateral support and resists racking.
Common variants and applications
Single-rabbet joints appear where one board is rabbeted and the other remains square; both boards are rabbeted in a double-rabbet setup, used in frame-and-panel construction and box making. The term sometimes covers the simpler case where only one rabbet exists, but the joint name properly applies to the assembled pair. Rabbets are standard in cabinet sides joining rails, in picture frames where the rabbet holds glass and backing, and in box bottoms slid into rabbeted walls.
The main failure mode is wood movement: seasonal humidity swings cause boards to expand and contract perpendicular to the grain, stressing the joint if it is glued without allowing seasonal play. A loose rabbet joint also fails to support lateral load; poor fit or insufficient rabbet depth lets the vertical plane shear. The rabbet's effectiveness depends entirely on a tight, snug fit and adequate glue coverage on both mating surfaces.
The term "rabbet" likely derives from the Old French "rabat," meaning a cut or notch, and the joint takes its name from the rabbet that defines it. It has been used in joinery for centuries and remains one of the most practical, visible joints in frame construction, less demanding than a mortise and tenon but more reliable than a simple butt joint.