While rummaging through the tools my Dad left me , I came A across a hand held measuring tool with the Words : Met-L-Scan trade mark and on the other side the Words : SNAPIT . It is a pistol Grip tool with a a rotary On & Off Switch in red , and a white plastic knob like a watch stem . It has a red light that turns on when you turn the rotary switch . Does anybody know what it is made to measure or test ? It uses a Standard 9V battery in the grip.