The Rafter Square
Laying out a roof with this basic tool and a new generation of accessories.
Synopsis: Here is a guide to using the rafter square for more than squaring up a board. The author outlines various calculations that can be carried out with tables printed on the square. Sidebars describe the Speed Square and a tool called the Squangle. A chart explains how to use a calculator for roof framing.
Few carpenters would neglect to include a steel square when packing their toolboxes for a job. Yet, when pressed, quite a few good builders will abashedly admit that they generally use the square just for scribing a cut-off line on stock too large for their combination square. The steel square can serve a variety of functions, from stairbuilding to making simple checks for right angles, but it’s especially useful for laying out rafters and other roof-frame members. With a little instruction, anyone can lay out cuts for common rafters, valleys, hips, jacks and gable ends. This doesn’t require a knowledge of trigonometry, just a simple understanding of the geometry involved.
The rafter square
This versatile tool consists of two parts — the body, or blade, and the tongue. These two meet at the heel. The body is 24 in. long and 2 in. wide, and usually represents the level line, or run, in laying out rafters. Plumb, or rise, is represented by the tongue, which is 16 in. long and 1 1/2 in. wide. The face and back of the square are usually imprinted with edge scales and math tables. The latter distinguish a rafter square from a framing square.
Squares are made of steel, usually painted black, or aluminum. Aluminum squares are typically more expensive, but lighter and less liable to bring second-degree burns to your palms on hot summer days. The best squares have their numbers stamped deeply into the metal rather than painted on. Most of…