Adjustable Triangles

The ADJUSTABLE TRIANGLEcombines the functions of the triangle and the protractor. When it is used as a right triangle, the hypotenuse can be set and locked at any desired angle to one of the bases. The transparent protractor portion is equivalent to a protractor graduated in 1/2° increments. The upper row of numbers indicates angles from  0° to 45° to the longer base; the lower row indicates angles from  45° to 90° to the shorter base. By holding either base against a T square or straightedge, you can measure or draw any angle between 0° and 90°.

The adjustable triangle is especially helpfulin drawing building roof pitches. It also allows you  to transfer parallel inclined lines by sliding the base along the T square or straightedge.