Zircon 61980 StudSensor Pro LCD Edge Stud Finder with Easy-to-Read LCD Screen and Spotlight Pointing System (61981) Find the edges of wood or metal studs or joists up to 1 1/2 in. (38 mm) deep WireWarning alert indicates the presence of hot electrical wiring Includes Zircon instructional "How-to Guide" Z-Card and detailed instructions. Sensing depth & accuracy can vary due to moisture, materials, wall text., paint. Not recommended for use on lath and plaster