How do you make wood joints such as the dovetail and mortise and tenon?
The Wood Guide · Do it yourself
TechniqueWood joints
Joining pieces of wood firmly without a single nail or screw. The three classics, and what to do when one breaks.
- Dovetail · mortise and tenon · box joint
- Without nails or screws
- Also: repairs
Joints in brief
Techniques for fixing wood to wood using the shape of the wood itself, not metal. They are the backbone of long-lasting furniture and structures.
The principle behind every good wood joint is the same: let the force run through the wood rather than through a screw. A screw acts on a single point and eventually works loose; a well-made dovetail gets tighter the harder you pull on it, because the wedge shape locks itself in place.
And there's a second reason they're still made: wood moves. Metal doesn't. A joint that lets the wood move survives a hundred changes of season; a rigidly screwed one doesn't.
The dovetail is mechanically locked: the wedge-shaped tails can only leave their sockets in one direction, and that's exactly the direction in which they aren't loaded in normal use. Pull on a dovetailed drawer front and the joint only locks tighter. That's why drawers have been made this way for centuries.
- Dovetail
- wedge-shaped tails in matching sockets
- Mortise and tenon
- a tenon in a cut-out mortise
- Box joint
- straight fingers that interlock
- Force
- runs through the wood, not through metal
- Advantage
- lets the wood move
- Tools
- fine handsaw, chisel, marking gauge
To be honest: hand-cut joints take time. A set of dovetails for one drawer is half an hour's work for a practised hand, an evening for a beginner. For a cabinet with eight drawers, that's a real trade-off — and exactly why most factory furniture has them machine-routed or simply screwed.
In pictures · The three classic joints
Schematic drawing.
The three classic joints
Dovetail
Wedge-shaped projections — the tails — fit exactly into matching sockets. Strong and beautiful, and the classic for drawers and fine furniture. Mark out both pieces, saw the tails with a fine handsaw, chop out the waste between them with a chisel, and keep paring until the joint is tight without forcing it.
Mortise and tenon
A tenon on one piece fits into a cut-out hole — the mortise — in the other. The most versatile joint there is: you'll find it in chairs, doors, window frames and timber framing. The rule is that the tenon is about a third of the thickness of the wood.
Box joint
Straight, equal fingers that interlock — also called a finger joint. Simpler than a dovetail but with a large glue surface, so very strong. Ideal for chests and boxes.
By hand or by machine
A hand-cut joint has uneven spacing and you can see it — some people find that's exactly its charm. Machine-routed joints are more regular and quicker, but recognisable by their identical spacing.
Always saw on the waste side of your line, not on it. A saw kerf is one to one and a half millimetres wide; saw down the middle of the line and your joint is too loose straight away. Better a hair too tight and pare it to fit with the chisel.
Repairing a broken joint
- 1 · Assess what's brokenHas the glue let go, or is the wood itself broken? Failed glue is easy; broken fibres mean patching or replacing.
- 2 · Take it fully apartHalf a repair doesn't work. On old furniture with hide glue, heat and moisture are enough; with modern PVA you have to prise carefully and sometimes sacrifice something.
- 3 · Remove the old glueNew glue won't bond to old glue. Scrape or sand both surfaces back to bare wood.
- 4 · Don't fill the gap with glueIf the tenon has become too loose, glue a thin veneer shim to its cheek instead of filling the cavity with glue. Glue without wood-to-wood contact is not a joint.
- 5 · Glue and clamp againOn antiques, use hide glue to keep the repair reversible. See which glue for what and restoring antique furniture.
It's tempting to screw a loose chair leg back in place. But the screw splits the tenon, blocks the wood's movement, and makes a proper repair later almost impossible. Do it right once instead of quickly three times.
Frequently asked questions about wood joints
Which wood joint is the strongest?
For tensile loads, the dovetail, because the wedge shape locks itself in place. For general construction, the mortise and tenon. The box joint scores on glue surface and is therefore strong under shear loads.
How thick should the tenon be in a mortise and tenon?
As a rule of thumb, about a third of the thickness of the wood. Thicker weakens the mortise, thinner weakens the tenon.
Why do I saw on the waste side of the line?
Because the saw kerf itself is one to one and a half millimetres wide. Saw on the line and you lose that width, making the joint too loose straight away.
How do I repair a joint that has come loose?
Take it apart, remove all the old glue, take up any slack with a veneer shim rather than glue, then glue and clamp again. Never drive a screw through it.
Joints in perspective
Let the force run through the wood — that's the whole art.
Have a question about your project? Just ask — we're happy to help.
Photos via Wikimedia Commons: Finished dovetail joint on the corner of a solid-wood workpiece — Emhoo, CC BY-SA 3.0 · National Library of Australia, Canberra — Sam Wilson, CC BY-SA 4.0 · Mortise cut into a windmill post, ready for the tenon of a brace — Rasbak, CC BY-SA 3.0
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