Irwin 6041705CD Strait-Line 150 Live Wire in Wall Sensor Accuscan technology is specifically calibrated for finding studs behind drywall, paneling or tile up to 1-1/2 inches thick Auto marking means no more pencil marks for cleaner surfaces Automatic on/off with surface contact for quick detection LCD screen shows exact location of stud as tool is moved over the surface for pinpoint accuracy Identifies metal studs and warns of live A/C wiring for safer electrical work and shelving