Half lap joint
A half lap joins two pieces by cutting away half the thickness of each where they overlap, so they sit together with their faces flush. Laps can join pieces at a corner, at a T, or crossing in the middle, and they show up in frames, stretchers, grids and workbench parts.
The geometry
Each piece loses exactly half its thickness over the width of the other piece. For two 3/4 in boards, each cheek is cut 3/8 in deep, and the width of each cut equals the width of the mating piece. When the two pieces are the same thickness, the same saw or bit height cuts both, which is why laps are quick to set up.
How it’s cut
On the table saw, a dado stack set to half the thickness clears the lap in a few passes, with the miter gauge or a sled guiding the piece and a stop setting the shoulder. A router with a straight bit and a guide does the same in larger work. By hand, saw the shoulder to depth, make a series of kerfs, and chisel the waste out, then pare the cheek flat.
Glue and strength
A lap glues face to face over a large area, with the grain of the two pieces crossing in a T or a cross lap. This site gives no strength numbers for laps: the published tests we found used different rigs.
Related joints
Sources
- Rockler, Woodworking furniture joinery: butt joints, mortise and tenon, dovetails, read 2026-11-07
Proportions marked as a traditional rule are shop tradition, not measurements. This site gives no joint-strength numbers: the published tests each used a different rig. How we source these numbers.