A wide variety of protractors and angle gages are available that vary in construction and application. Angle squares consist of a square with angular graduations along the longest face or hypotenuse.

While only one patent model for a protractor survives in the Smithsonian collections—from an inventor with a colorful personal history—several of the other objects also provide examples of technical ...

Centre the protractor on the same end of the line and make a dot at 40°. From the same end, use a ruler to draw a line through the dot, crossing the arc. Label the length 7 cm and the angle 40°.