Amazon.com Product Description

The Stud 4 Sure is a stud finder that uses powerful rare earth magnets to pinpoint the exact location of screws or nails in a stud. The tool doesn’t require batteries and never needs calibration. By keeping the tool free of moving or electronic parts, the Stud 4 Sure is easy to use and fits easily into any tool pouch. Just place the stud finder on the wall and sweep in an "S" pattern to locate any metal fastener. The rare earth magnets are strong enough to allow Stud 4 Sure to hang hands-free on a wall, eliminating the need for pencil markings. The ergonomically designed, China made product is guaranteed to last a lifetime of being tossed, dropped, and banged around.