For the production of single-piece and small-volume mechanical parts, there are no special tools, clamps, molds, and no special inspection and measuring tools. Therefore, the length and position dimensional tolerances of IT7 and above are commonly used for vernier calipers and depth gauges, but due to measurement. Errors and visual errors, and the test results and processing quality are difficult to meet the design requirements. The measuring block is a high-precision universal inspection tool for detecting the length dimension. It is applied to the first inspection of the parts at the processing site, and the quasi-determination of the work, clamps and tools.