A protractor is a transparent plastic tool designed to measure angles. They are usually semicircular but also are available in a full circle 360° version.
|Origin||The small hole near the bottom of the protractor is aligned over the vertex of the angle to be measured.|
|Baseline||The line along the bottom of the protractor is aligned along one of the angle's legs.
Note: It is not the edge of the protractor body itself, but parallel to it.
|Scales||The angle of the other leg is read from one of the two scales, whichever is more convenient.|