The bevel protractor is used to establish and test angles to very close tolerances. It reads to 5 minutes or 1/20^o and can be used completely through 360^o.

The bevel protractor consists of a beam, graduated dial and blade, which is connected to swivel plate (with Vernier scale) by thumb nut and clamp. When the edges of the beam and blade are parallel, a small line on the swivel plate coincides with the zero line on the graduated dial, and when any measurement of an angle between the beam and the blade of 90 degrees or under is desired, the reading may be obtained direct from the position of the line on the swivel plate with regard to the graduation numbers on the dial.