Product Description Stanley 47-400 This Magnetic Stud Finder is 1-3/8" x 1-3/8" x 1-1/4"(35mm x 35mm x 32mm). Provides dependable detection of wall studs. Magnet works by locating steel nails and screws used to hold drywall to studs. Base of the stud finder is notched for convenient marking once studs are located. From the Manufacturer Provides dependable detection of wall studs. Magnet works by locating steel nails and screws used to hold drywall to studs. Base of the stud finder is notched for convenient marking once studs are located.