A mortise gauge is specifically designed to mark out mortises. It has two pins adjacent to one another which mark the mortise.
A mortise is a piece cut out of a larger piece of wood, so that a matching, separate piece (a tenon) can be inserted, a bit like a jigsaw. These are used when strength is important such as in window, door, chair or bed frames.
The mortise gauge is sometimes known as a combination gauge, because as well as its two mortise pins, it also has a third pin on the opposite side which can be used for regular marking.
Of the pins for marking out a mortise, the pin closest to the fence is adjusted using a screw which moves the pin either closer or further away from the other pin to match the mortise size.
Mortise gauge sizes
The mortise gauge is available with a stem length of between 152.4mm (6″) and 290.5mm (11.4″).
