Steel Square

The steel square is a carpentry tool built as a long, wide arm, called the body, meeting a shorter, narrower arm, called the tongue, at a right angle, used to lay out square corners and, through the graduations and tables commonly stamped along its arms, to work out the angles and lengths needed for rafters, stairs and other layout problems by calculation rather than trial and error. Though it takes its name from having traditionally been forged of steel, modern versions of the same tool are also made from aluminum or polymer, the name having stuck to the tool's distinctive long-armed shape rather than to the material it happens to be made from.