The standard "GB/T 11378-2005 Metal overlay, overlay film thickness measurement Profile Gauge method" introduces a Profile Gauge method for the measurement of film thickness of metal overlay. The method determines the film thickness of the overlay by forming a step between the surface of the overlay and the surface of the base metal and using a profilograph to measure the height of the step. It is suitable for metal overlay with film thickness ranging from 0.01 microns to 1,000 microns and is particularly suitable for the measurement of micro Film thickness. The standard specifies in detail the instrument characteristics and measurement procedures, which are suitable for flat surfaces and can be used for measurement of cylindrical surfaces after appropriate measures are taken. Note that if the film thickness of the cover layer is less than 0.01 microns, it is necessary to strictly control the surface flatness and smoothness.