A vernier caliper is used for measuring the distance between two sides. Thais always called it " vernier ". The vernier has more accuracy and precision than a ruler. First, a vernier has outside jaws and inside jaws which are used for measuring external and internal length respectively. Second vernier has the depth probe to measure depth. Third, there are two main scales in centimeter and inches. Next, there are two main vernier scales in centimeter and inches. Finally, the vernier has a part retainer which is used for locking or releasing the sliding scale.