Combination square - Definition and Overview

A combination square is a woodworking tool used for multiple purposes. The Square refers to the primary use of the tool: measuring the accuracy of a right angle (90°).

The tool is composed of primarily two parts: a rule and a head.

Uses

• Measuring angles — A combination square can be used to measure a 90° and a 45° angle. The 45° angle is used most commonly in miter cuts.
• Determining flatness — When working wood, a first step is to develop a reference surface on a board. From this reference surface, all else in the workpiece is measured. The rule of the combination square is assumed to be flat.

In woodworking, the starting raw material is neither flat nor square, however, the end product (e.g. a table) must be flat and have corners and legs that are square. Woodworkers utilize a reference surface to create and measure flatness. Their workbench is usually considered a reference surface (thus flat) and can be used to initially create a flat surface. However, the combination square is a more precise measurement and is used in these initial steps of woodworking to create and mark a reference surface and reference edge from which all other forms of the work will be measured from and must rely upon.