Mortise and Tenon Joinery: The Joint That Holds Furniture Together for Centuries

If joints were a family, the mortise and tenon would be the grandparent who has seen everything. It holds together Egyptian furniture, medieval timber frames and the chair you’re probably sitting on. It’s simple in concept — a tongue in a hole — and endlessly refined in practice.

The reason it lasts is mechanical: a tenon locked inside a mortise resists racking from every direction, and the long-grain glue surfaces on the cheeks bond almost as strongly as the wood itself.

Anatomy of the joint

• Mortise — the rectangular hole, usually in the leg or stile.
• Tenon — the projecting tongue on the end of the rail.
• Cheeks — the wide faces of the tenon; the main glue surface.
• Shoulders — the cut faces that butt against the mortised part and hide the joint.

Proportions that work

Beginner tip: size the tenon to a chisel you own. A 1/4" mortise chopped with a 1/4" chisel automatically comes out the right width.

Step 1: Layout

Precise layout is half the joint. Set a marking gauge once and use it for both mortise and tenon, always referencing from the same face. Mark shoulders with a marking knife and a square — the knife line gives your saw and chisel a crisp starting groove.

Mark a reference face and edge on every part with a pencil “face mark”. Gauge every line from those surfaces and small thickness differences won’t matter.

Step 2: Cut the mortise

By hand

1. Clamp the leg firmly over a solid part of the bench.
2. Start chopping in the middle of the mortise with the chisel’s bevel facing the centre.
3. Work toward each end in 1/8" steps, levering out waste as you go.
4. Stop just short of the end lines, then make final vertical chops right on the lines.

With machines

Drill a row of overlapping holes on a drill press using a Forstner bit, then pare the walls square. Or rout the mortise with a plunge router and edge guide and square the ends with a chisel.

Step 3: Cut the tenon

Saw the shoulders first, just on the waste side of the knife line. Then saw the cheeks, staying slightly fat — you’ll pare to fit. On a table saw, a tenoning jig or a dado stack with a stop block makes identical tenons quickly; see our table saw jigs guide.

Step 4: Fit the joint

The goal: the tenon slides in with firm hand pressure and stays put if you lift the assembly. Pare or plane the cheeks a few strokes at a time, testing frequently. Chamfer the end of the tenon slightly so it enters cleanly.

Don’t hammer a tight tenon home. Wood swells with glue, and an over-tight joint can split the mortise walls — especially near the end of a leg.

Step 5: Glue up

Spread glue on the mortise walls and tenon cheeks, assemble and clamp across the shoulders. A long-open-time glue gives you time on complex assemblies.

Variations worth knowing

• Haunched tenon — a short stub fills the groove in frame-and-panel doors.
• Through-tenon — visible on the outside; can be wedged for decoration and strength.
• Drawbored tenon — an offset peg pulls the joint tight with no clamps. See our drawboring guide.
• Loose tenon — two mortises joined by a separate tenon strip; quick with a router.

Beginner, intermediate, pro

Beginner: practise on poplar or pine. Cut three joints in an afternoon and compare.

Intermediate: build a table base. The walnut dining table guide uses mortise and tenon throughout.

Pro note: on a table leg, offset the mortises so the tenons from adjacent aprons don’t meet; mitre the tenon ends where they do. You’ll keep maximum glue surface and tenon length.

Explore the rest of the joinery family in our complete guide to woodworking joints.