A depth gage could be as simple as marks on a piece of tape, a line on a ruler, or tape on a drill. Fortunately, of course, modern gages take the guesswork out of measurement, providing a range of simple or high-tech options depending on the job.
The measurement of the depth of a hole sounds straightforward and simple. In many cases it is. In others, there are design features of both the part and the gage that must be considered to insure an accurate measurement and a properly assembled or functioning part.