Combination square

A combination square is a multi-purpose measuring and marking tool used in metalworking, woodworking, and stonemasonry.

The head is then tightened in place via a lock bolt or lock nut which engages with a channel running the full length of the rule, allowing the head to be tightened on at any point along the rule.

Aluminium and zinc heads are cheaper than steel and iron, but less durable and more prone to inaccuracy.

[note 1][8] In 1880 he founded the L. S. Starrett Company in Athol, Massachusetts, United States.

The tool was originally designed for machinists, but over time became commonly used in other trades, such as woodworking.

A combination set with the rule (top), a standard head (left), protractor head (centre), and a centre finder head (right).
Illustration showing a centre head, protractor head, and standard head attached to a rule.
Labelled diagram of the standard head
Labelled diagram of the protractor head
Labelled diagram of the centre finder head with a circle as an example