How to use bore guage

Bore Guage-A gauge, in science and engineering, is a device used to make measurements or in order to display certain dimensional information. A wide variety of tools exist which serve such functions, ranging from simple pieces of material against which sizes can be measured to complex pieces of machinery. Depending on usage, a gauge can be described as "a device for measuring a physical quantity",For example "to determine thickness, gap in space, diameter of materials, or pressure of flow",

or "a device that displays the measurement of a monitored system by the use of a needle or pointer that moves along a calibrated scale".