Mortise and tenon

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See Tenon Limited for the New Zealand "Wood Solutions" company.

Diagram of a Mortise and Tenon Joint

Simple and strong, the mortise and tenon joint (also called the mortice and tenon) has been used for millennia by woodworkers around the world to join two pieces of wood, most often at an angle close to 90°. Although there are many variations on the theme, the basic idea is that end of one of the members is inserted into a hole cut in the other member. The end of the first member is called the tenon, and it is usually narrowed with respect to the rest of the piece. The hole in the second member is called the mortise. The joint may be glued, pinned, or wedged to lock it in place.

A mortise is a cavity cut into a timber to receive a tenon.

There are several kinds of mortises:

Open mortise - a mortise which has only three sides. (See Bridle joint).
Stub mortise - a shallow mortise, depth depends on the size of the timber; also a mortise that does not go through the workpiece (as opposed to a "through mortise").
Through mortise - a mortise which passes entirely through a piece.
Wedged half-dovetail - a mortise where the back is wider, or taller, than the front, or opening. The space for the wedge initially allows room for the tenon to be inserted, the presence of the wedge, after the tenon has been engaged, prevents its withdrawal.
Through wedged half-dovetail - a wedged half-dovetail mortise which passes entirely through the piece.

A tenon is a projection on the end of a timber for insertion into a mortise. Usually the tenon is taller than it is wide.

There are several kinds of tenons:

Stub tenon - a short tenon; depth depends on the size of the timber; also a tenon that is shorter than the width of the mortised piece so the tenon does not show (as opposed to a "through tenon").
Tusk tenon - a kind of mortise and tenon joint that uses a wedge-shaped key to hold the joint together
Through tenon - a tenon which passes entirely through the piece of wood it is inserted into, being clearly visible on the back side
Teasel tenon - a term used for the tenon on top of a jowled or gunstock post, which is typically received by the mortise in the underside of a tie beam. A common element of the English tying joint
Top tenon - the tenon which occurs on top of a post.
Feather Tenon - a round shouldered machined fillet or feather which is glued into a machine (router) made slot or mortise on each side of the joint.

Generally the size of the mortice and tenon is related to the thickness of the timbers. It is considered good practice to proportion the tenon as 1/3rd the thickness of the rail, or as close to this as is practical.