●Scanning technology accurately detects and locates wood and metal studs, beams and joists behind plywood and drywall. ●Audio and LED display detects stud and joist edges. ●Slide STUD SENSOR across surface. ●The Stud Sensor uses electronic signals to locate the edges of studs, joists or live AC wires through drywall or other common building materials. Once the edge of a stud has been detected, the Stud Sensor displays two red LED’s and sounds an audible tone. A pencil notch allows you to easily note the stud edges on the wall.