A mortise gauge or mortice 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
Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...
with brass fittings.
Like the simpler
marking gauge
A marking gauge, also known as a scratch gauge, is used in woodworking and metalworking to mark out lines for cutting or other operations. The purpose of the gauge is to scribe a line parallel to a reference edge or surface. It is used in joiner ...
, 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",
[The Mortise Gauge]
''Technology Student'' 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.
Some mortise gauges are designed with one retractable spur, so that they can be used as marking gauges as well;
A Short Guide to Mortise and Marking Gauges
''Tools for Working Wood'' however, because the mortise gauge is an expensive and high precision tool, many carpenters prefer to have a separate marking gauge for general use.
References
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Woodworking measuring instruments