Biscuits, dowels or dominoes — which should I use?

All three do the same thing conceptually: a separate piece of wood spans the joint line and sits in a matching recess in each part. What separates them is how much glue surface they contribute and how much accuracy they demand from you.

Step by step

1. Decide whether you need alignment or strength.An edge joint between two boards already has all the strength it needs from long-grain glue surface. What you want there is alignment, so biscuits are the right tool and dowels are a waste of effort.
2. For carcass work in sheet material, choose alignment and speed.Biscuits or a loose tenon. The glue area of the joint face does most of the work in MDF or ply, and the biscuit stops the parts sliding while you clamp.
3. For frames that will be racked, choose strength.Chair rails, table frames, doors and gates need long grain into long grain across the joint. Loose tenons or real mortise and tenons. Biscuits are not adequate here.
4. For end-grain joints, nothing loose will save a bad joint.End grain glues poorly whatever you put across it. Two dowels or a loose tenon convert an end-grain butt into a joint with real long-grain surfaces — that is the whole point of using them there.
5. Match the method to your accuracy.If you are working without a bench and a reliable square, dowels will frustrate you. Biscuits tolerate a millimetre of error; dowels tolerate almost none.
6. Cost it honestly before buying.A dowel jig is the cheapest entry, a biscuit joiner is a moderate tool, a loose tenon machine is a large purchase. Buy the one that suits the work you actually do repeatedly, not the best one.

Tips

• Dowels are still the standard in mass-produced furniture precisely because a machine can drill them perfectly. Done by hand with a self-centring jig they are excellent; done by eye they are miserable.
• You can make loose tenons without the branded machine — rout a mortise in each part with a straight bit and a jig, and make a strip of tenon stock to fit. It is slower but structurally identical.
• If you already own a router, a simple mortising jig gets you loose tenon joinery for the price of a cutter.

Alternatives

• Biscuits: Compressed beech ovals in a curved slot. The slot is longer than the biscuit, so there is sideways adjustment — very forgiving. Fast, cheap, excellent for aligning cabinet parts and edge joints. Adds only marginal strength.
• Dowels: Round pins in drilled holes. Genuinely strengthen a joint, resist racking, and locate in every direction with no adjustment at all — which is also the drawback, because two holes that are half a millimetre out will not go together. Cheapest to start with if you buy a jig.
• Loose tenons (Domino and similar): A flat floating tenon in a routed mortise. Structurally equivalent to a traditional mortise and tenon, with adjustable-width mortises so there is alignment tolerance. The machine is a serious purchase; the joints are as good as anything short of hand-cut.
• Pocket holes: Not a loose tenon at all, but the fourth thing people choose between. A screw driven at an angle through one part into another. Fast, needs no clamping, and leaves a visible hole — strong in the right orientation, poor in the wrong one.

Questions people ask