API Caliper is used for general-purpose measurements, both in the clinic or for other purposes, to establish an accurate measurement, e.g., internal and external diameter, length, depth or thickness A Boley gauge is an instrument used in dentistry for measuring teeth and space. Boley Gauge helps in determining tooth dimensions of length, width, and thickness. The flat end is good for measuring teeth size and distance of spaces in the mouth. Boley gauges are accurate to tenths of a millimeter. A Boley gauge has a fixed scale and a sliding scale. Metal caliper is used by dentist for measuring thickness of a metal, so that caliper has a pointed tip. Wax caliper is used by the dentist to measure the accuracy of wax crown pattern, so that caliper has a rounded tip.