Block gauges are also called rule blocks. One block represents one size. A set usually contains dozens to hundreds of blocks of different sizes. They are standard tools for precise length measurement. They are made of wear-resistant materials such as alloy steel, tool steel, tungsten steel, and ceramics. They are usually rectangular in shape, and two opposite sides of the six faces are used for measurement. They are made with very high processing accuracy and must be cleaned before use. When measuring, crimp two or more block gauges together and measure the length.