The workshops of machine and instrument engineering aim to produce products of high work quality. Therefore, the individual parts must not only have the same dimensions within permissible limits but also exhibit a surface quality that meets the requirements for the future cooperation of two parts, whether they work together with play, sliding, or stationary fits. Twenty years of diligent development work by all technically advanced nations have created testing methods and instruments that have thoroughly clarified this challenging field both theoretically and practically. Numerous workshops on the European mainland, in England, and in the United States either rely on accurate measurement of quality or on a comparative assessment of the workpieces against proven sample parts.