US Patent 10197639 Ferromagnetic fastener locating device

For locating a ferromagnetic object, a device has a non-magnetic housing with a perimeter wall, a front surface, and a rear surface. The perimeter wall defines a chamber within the housing. A stop element is located within the chamber between the front surface and the rear surface. A magnet element is housed within the chamber and is movable between a resting position, where the magnet element is proximate the stop element, and an active position, where the magnet element is proximate the front surface. The device has a mechanism for returning the magnet element to the resting position in the absence of a ferromagnetic object located proximate the front end of the device.