Abstract: A depth gauge includes a number of alternating sections of material which are X-ray transparent and X-ray opaque, respectively. The sections are carried in an elongated cylinder, and are each of a predetermined known length. The depth gauge is insertable into a hole or cavity to be measured, and viewed with X-ray techniques, from any angle. The number of sections of X-ray transparent and opaque material being within the hole, as seen by the X-ray techniques, indicate the depth into the hole which the pin is inserted. In one embodiment, a drill point is included on the end of the elongated cylinder to enable the depth gauge to be used additionally as a drill, so that depth to which the drill has cut can be monitored during the drilling process, if desired.