The combination square set consist of a blade (graduated steel ruler) and moving heads called a square head, protractor and a center head.
The blade is designed to allow the different heads to slide along the blade and be clamped at any desired location. By removing all the heads, the blade may be used alone as a rule or a straight edge. This tool, with its attachments, may be used for a great many purposes in framing and general work.
The blade (steel ruler) can be used as a ruler or a straight edge by itself or with any one of the following components.
The square head is designed with a 45 and 90 edge, which makes it possible to be used as a try square and miter square. It may also be used as a height or depth gauge. The square head is also fitted with a level vial and a removable scriber.
Various uses of the square head
Laying out parallel lines with a combination square
The center head can be used to locate and lay out the exact center of round stock.
The protractor head can be used to mark off or measure any angle through 180. Angular graduations usually read from 0 to 180 degrees both ways, permitting the supplement of the angle to be read.