The stanley intelli tools stud sensor 100 uses electronic signals to locate edges of studs joists or live ac wires through drywall or other common building materials once the edge of the stud has been detected the stud sensor 100 displays red leds and sounds an audible tone a v shaped marking channel with an led allows accurate marking the ergonomic design and soft grips ensure a comfortable use detection depth wood and metal stud detection up to 19mm ac detection up to 50mm uses a std 9v batter