Vernier caliper is the most used device to measure pieces in workshops. The caliper is able to perform outside measurements, inside measurements, and depth measurements.
Normally the main body is the fixed part bearing the main graduation, while another one is the mobile part, called Vernier. The Vernier has a locking system (called brake) in order to avoid accidentally losing the measurement during the instrument manipulation. There is usually a frictioning button or a locking screw. The range of caliper is the maximum opening of the device. Measurements have an approximation that can be 1/10, 1/20 or 1/50 mm, depending on the type of caliper.
The material used for the caliper construction is generally hardened stainless steel, which has excellent non-deformability quality and resistance to wear.