A marking gauge with two adjustable pins, used to score two parallel lines simultaneously for laying out mortises and tenons.
Set the mortise gauge off the chisel — no measurements involved.
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 projecting tongue cut on the end of one piece, sized to fit a matching mortise. The male half of a mortise-and-tenon joint.