Most Round or Circular Protractors are considered school supplies, but many people on the job still use Protractors today. Protractors are measuring instruments for measuring angles. Most protractors measure angles in degrees and go from 0 to 180 degrees. Most protractors are made of transparent plastic and are designed to be laid flat on a drawing or any thing that has 2 lines were an angle can be measured. Most people first learn of a protractor and how its used in school, usually in math class and to be more specific, geometry class. Some people call protractors "Angle Finders" although not the technical name.