Mortice and tenon

A mortice (or mortise) and tenon joint is a type of joint that connects two pieces of wood or other material. Carpenters have used it for thousands of years to join pieces of wood. It is used when the adjoining pieces connect at an angle of 90°. 
In its basic form, it is simple and strong. There are many variations. The basic mortice and tenon has two parts: the mortice hole and the tenon tongue. The tenon, on the end of a member (called a rail), fits into a square or rectangular hole in the corresponding member. The tenon is cut to fit the mortice hole exactly and usually has shoulders that seat when the joint fully enters the mortice hole. The joint may be glued, pinned, or wedged to lock it in place.
This joint is also used with other materials. For example, it is a traditional method for stonemasons and blacksmiths.