Figure 1 shows a kind of workpiece produced by our factory in batch production. The technical requirement is that the distance between the M face of the four M-shaped ports to the corresponding four screw holes φ40_(0.10)~(+0.16)mm is 45H11 (_0~ (+0.16))mm, and meet the requirement of parallelity tolerance of 0.10, and quantitative measurement is required in the production process.