Portable Wall Tester Stud Sensor Metal Joists Detector Handheld Finder Screw Edges Finder with LED Indicator This wall metal detector is crafted from quality material, shock-resistant, and wear-resistant, can provide long service time. Uses an electronic signal to locate the edges of a stud or joist,  and its signal can pass through drywall and plywood, and the designed depth is up to 3/4inches. Easy e, when it detects the edges of the stud, the red LED will light up and make a sound. Wide applications, suitable for different wall appearances such as wall siding, wallpapered wood floors, sound-absorbing ceilings, painted walls, etc. Features: Crafted from quality material, shock-resistant, and wear-resistant, can provide long service time. Uses an electronic signal to locate the edges of a stud or joist,  and its signal can pass through drywall and plywood, and the designed depth is up to 3/4inches. Easy e, when it detects the edges of the stud, the red LED will light up and make a sound. Use the handy pencil notch located at the upper of the unit to mark the stud edges. Repeat from the other side of the stud. Coming from the opposite direction, mark the other edges of the stud. The midpoint of the two marks indicates the stud center. Wide applications, suitable for different wall appearances such as wall siding, wallpapered wood floors, sound-absorbing ceilings, painted walls, etc. Note: While calibrating, the stud sensor can not be placed directly over a stud, dense material such as metal, or over a wet or newly painted area, or it will not properly calibrate. Specifications: Name: Wall Metal Detector Material: plastics Battery: 1 * 9V battery (not included) Color: red, orange, yellow, blue (optional) Item size: 136 * 23 * 50mm / 5.35 * 0.91 * 1.97in Item weight: 80g / ounce Package size: 144 * 26 * 55mm / 5.67 * 1.02 * 2.17in Package weight: 90g / 2.82ounce Packing List: 1 * Wall Metal Detector