Protractors are measuring tools used for measuring and marking angles, usually in degrees. They consist of a flat, semicircular, or circular base with a calibrated scale from 0° to 180° or 360°, and a movable arm or straight edge that aligns with the desired angle. Protractors are often used in drafting, engineering, carpentry, and metalworking to ensure accurate angle measurements and cuts. Digital protractors are also available, offering precise electronic readings.