Point-man Aeronautic's, llc., along with the FAA and other industry standard organizations and documentation, STRONGLY recommends that tools used in aerospace maintenance, production, testing and repair be calibrated to assure compliance with the regulation (AD2011-10-09 in this case). Repair Stations and production facilities are required by the FAA to calibrate, and maintain calibration records for all measurement and test tools; this includes the TOMKEY.

Remove the carpet from the area of the hole in question and use a mirror to note depth gauge position. Making a few pencil/fine tip marker marks on the rail hole below the rail surface will help in remembering its position.