A projecting tongue cut on the end of one piece, sized to fit a matching mortise. The male half of a mortise-and-tenon joint.
Trim the tenon cheeks until it slips home with hand pressure.
A rectangular hole cut into one piece to receive a matching tenon from another. The female half of the strongest traditional joint in furniture.
A traditional technique where a peg is driven through a tenon and into the mortise at a slight offset, pulling the shoulders tight permanently without clamps.