A reproduction of an antique tool from the Lee Valley collection, this square simplifies the often-complex layout of both rafters and miter joints.

The original, patented in 1914, resembles a speed square but with a movable fence that can be locked at various standard miter, rafter and hip rafter angles. To fix an angle setting, a sliding pointer on the pivoting fence is set to register in the holes of one of the three scales. Tightening the brass thumbscrew then locks the pointer and fence in position.

For laying out the plumb cuts for common or hip rafters, as well as the end cuts of collar ties, you can select pitches from 1 to 12 (for example, the #4 common rafter setting gives a 4/12 pitch), then mark your line directly from the square – no calculations or rafter tables needed, and you don’t have to keep reading a printed/etched scale.

The 13 miter indexing holes, numbered from 4 to 24, set the miter angles needed to create polygons with the corresponding number of sides. For example, the #4 setting indicates the 45° angles needed to create a four-sided construction, #8 gives the 22.5° angles needed for octagons, and so on.

The square is 11 1/4" along the hypotenuse, with a 10 1/4" pivoting fence and an 8" fixed fence that measure 5/16" thick for reliable registration against your work. For the angle settings on the front as well as the Imperial scale on the back, it has dark etched markings for contrast against the stainless-steel blade.

Deceptively simple in design, it has an array of complex geometry built right into it. Made in Canada.