原空間

（引用自：http://phoenix.phys.clemson.edu/labs/cupol/vernier/index.html）

A vernier caliper (or vernier) is a common tool used in laboratories and industries to accurately determine the fraction part of the least count division. The vernier is a convenient tool to use when measuring the length of an object, the outer diameter (OD) of a round or cylindrical object, the inner diameter (ID) of a pipe, and the depth of a hole. To see short videos showing how to use the vernier to measure these various dimensions,

 

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（引用自：http://en.wikipedia.org/wiki/Caliper）

A caliper (British spelling also calliper) is a device used to measure the distance between two symmetrically opposing sides. A caliper can be as simple as a compass with inward or outward-facing points. The tips of the caliper are adjusted to fit across the points to be measured, the caliper is then removed and the distance read by measuring between the tips with a measuring tool, such as a ruler.

 

They are used in many fields such as metalworking, mechanical engineering, gunsmithing, handloading,woodworking and woodturning.