What is a bridle joint?
A bridle joint is a wood joint in which a tenon fits into a slot that is open at the end of the other piece, so that three or more faces are glued together. It is also called an open mortise and tenon or slot mortise and tenon. The Dutch term “slisverbinding” covers the same joint and its multi-tongue versions. It is typical of window frames, chairs and tables.
Construction and variations
One piece gets an open slot at its end (the fork), the other a tongue that fits it exactly. Because the slot is open, both parts can be cut entirely with a saw.
- Corner bridle. One tongue, one slot, three glue faces.
- T-bridle. The slotted piece straddles a tongue cut in the middle of the other rail.
- Multiple bridle. Several interlocking tongues with a fork that has three openings. More glue area, more strength.
- Pinned. A dowel drilled and glued through the corner adds mechanical security.
Difference from mortise and tenon: in a standard mortise and tenon the tenon is enclosed in a closed mortise and hardly visible. In a bridle joint the slot is open and the joint shows on two faces. The large glue area makes it strong, but it relies on a good fit.
Application
- Mark out. Divide the thickness into three equal parts (or more for a multiple bridle). Use a mortise gauge on both pieces from the same reference face.
- Saw. Always cut on the waste side of the line. A bandsaw or a table saw with a tenoning jig gives the straightest slots.
- Chop out. Remove the waste from the slot with a chisel, working from both faces to the middle.
- Dry fit. The tongue should slide in with light hand pressure. Too tight splits the fork; too loose leaves a weak glue line.
- Glue and clamp. Glue all faces, clamp in both directions and check for square. Use a water-resistant wood glue outdoors.
Common mistake: making the fork cheeks too thin. They split when clamped or later under load.
Related terms
- Mortise and tenon joint
- Wood joints
- Dovetail joint
- Half-lap joint
- Wood glue
- Dowel
- Window frame
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