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.