Gauge blocks are blocks used for testing and calibrating certain measuring instruments and test equipment, but can also be used as secondary standards in direct measurement. They are characterized by high accuracy with respect to their dimensional scale. Gauge blocks come in various forms. Gauge blocks are one of them. They are cuboid blocks with high length accuracy. Thanks to their high surface quality, they can be placed together by adhesive forces, although they should be separated again after a few hours to avoid cold welding. Of the linear measuring standards, gauge blocks represent those with the smallest measurement uncertainties. In addition to gauge blocks, there are also angle, spherical, cylindrical or step gauge blocks. Gauge blocks are usually made of steel, which, however, requires a high degree of maintenance. Gauge blocks made of hard metal are more resistant to wear, but have less favorable thermal expansion properties than steel. Gauge blocks made of ceramics are characterized by particularly high wear resistance, favorable thermal expansion and low weight as well as low maintenance requirements.