GAGE, in joinery, is an instrument made to strike a line truly parallel to the straight side of any board or piece of stuff. Its chief use is for gaging of tenons true, to fit into mortises; and for gaging stuff of an equal thickness. It is made of an oval piece of wood, fitted upon a square stick, to slide up and down flitly thereon, and with a tooth at the end of a staff, to score, to strike a line upon the staff at any distance, according to the distance of the oval from it.