The Arabs divided the Boxer into 180 parts, and the horn system was born. Then Arabs make protractors according to the angle system, and theory guides practice. There is also an arc protractor. Due to the development of commerce and architecture in BC, protractors also developed in various forms. Now, as a drawing tool, protractor is generally made of plastic or iron, which can draw the desired angle as needed and is often used with compasses. You can draw angles, measure angles, draw vertical lines and parallel lines, measure inclination, verticality and levelness, open and close with internal and external right-angle crutches, and make long and short rulers, which can be visually read out more accurately and draw a circle with a specified size.