在制造大量机件的场合,我们要使出品有互换或交替使用的可能,往往需要将出品精密地校验过。并且,精密制作的机件,或者形状很特殊的制件,也必须设法验明它是否适合于设计的尺度形态,否则也许有不能装配或使用的问题发生。在前面这种情形,我们用各种规尺(Gages),在后者则用样板(Templates)。但是规尺和样板,往往不能达到我们预期的准确度,而且同时也不能适用于机件形状很奇异 In the case of manufacturing a large number of parts, we must make the products have the possibility of interchangeable or alternate use, often need to carefully calibrate the production. Moreover, precision-made parts, or parts with very special shapes, must also try to find out whether it is suitable for the scale of the design, otherwise there may be problems that cannot be assembled or used. In the previous case, we used various gauges (Gages), and in the latter we used Templates. However, rules and templates often fail to achieve the accuracy we expect, and at the same time, they cannot be applied to the very strange shape of parts.