TRIANGLES, OR SET-SQUARES.
Set-squares are invariably used in connection with the tee-square, as shown in [fig. 148]. The illustrations below show several patterns of the device; by these, vertical lines, triangles, squares and hexagonal, octagonal and twelve-sided figures, diagonal section lines, etc., can be easily drawn. For ordinary purposes, a triangle or set-square with angles of 45° may be 4 inches long and the other 8 inches in length, but a six-inch set-square having angles 90°, 45° and 45°, and an eight-inch one having angles of 90°, 60° and 30°, will be found sufficient for all purposes; there are other triangles used specially for making letters.
Fig. 153.—Fig. 154.—Fig. 155.—Fig. 156.
In practice the triangles or set-squares are slid along the edge of the blade, and need not be any thicker than it.