Stud Finder, 4 in 1 Multi Function Wall Scanner Professional Wall Center Sensor Detector for Studs, Metal, Wood, and Live AC Wire 4 IN 1 WIDE APPLICATION  This wall detector built in 4 in 1 design to meet all the needs of home wall DIY projects. The STUD mode is for finding and locating the center and edges of wood and metal studs up to 34 in. (19 mm) deep. DEEP mode is for scanning walls for 1.5in (38mm) deep studs. METAL mode is for locating metal (such as 12 inch rebar) up to 2.36 in. (60 mm) deep. And AC mode is for locating live AC wires up to 2 in (51mm) deep. AUTOMATIC CALIBRATION The stud finder would calibrate itself automatically when it is turned on. The calibration is done by positioning the device on the wall where there is no wood studs, AC wires or metal. The stud finder will indicate whether it has been already calibrated or not. The automatic calibration is accurate and precise, providing users with maximum reliability, greatly reducing errors in application and makes sure that most objects behind the wall can be detected. SOUND ALERT - The multi function stud finder offers smart beep function, which beep alert continually to remind you of the location of the stud center detected. GRAPHICAL LCD DISPLAY  Built-in backlit digital LCD screen, which indicates many cues in detection, such as detection mode, signal strength, automatic calibration & battery power indication, its easier to help you read and operate it when using this wall scanner. HOW TO USE  With two buttons design helps you to understand and use it easily. The switch button on the middle of the device is used for selecting from the 4 scanning modes. Then press the button on the left side to automatic calibration and after scan horizontally across the object surface. Keep going until you find the location of the target and watch out the LCD screen indicated & BEEP sound alert. Use the pencil to mark the accurate location.