Adjustable height gauge is a type of measuring tool. In actual production, it is difficult to measure large quantities of products one by one using measuring tools (such as vernier calipers, micrometers, and other graduated measuring tools). The adjustable height gauge is divided into two measuring tools: the through gauge and the stop gauge. We know that qualified products have a measurement range, and those within this range are all qualified, so people adopt both general and stop gauges for measurement. For example, the thread height gauge of M6-7h has one end as a through gauge (T). If it can be smoothly screwed into the tested threaded hole, it is qualified. Otherwise, if it is unqualified, it needs to be reworked (i.e. the hole is too small). Then, if the adjustable high-low gauge (Z) can be smoothly screwed into the tested threaded hole by 2.5 turns or more, it is considered unqualified; otherwise, it is qualified. And at this time, the unqualified threaded holes should be scrapped and cannot be reworked. Among them, 2.5 rolls are the standard. If there are too many exported parts, only 1.5 turns can be made (standard). In short, the adjustable high-low gauge passing through the gauge is only qualified, and passing through both the gauge and the gauge is unqualified.