Mortice Gauge

A mortise gauge is a woodworking tool used by a carpenter or joiner to scribe mortise and tenon joints on wood prior to cutting. Mortise gauges are commonly made of hardwood with brass fittings.

Like the simpler marking gauge, a mortise gauge has a locking thumb screw slide for adjusting the distance of the scribe from the edge of the wood. It has two protruding pins, often called "spurs", which are designed to scribe parallel lines marking both sides of a mortise at the same time. One of the pins is adjustable, attached to a sliding fence, so that mortises of different widths can be marked.