Abstract: An improved sensor includes an inductor coil which is formed about a central axis. The inductor coil is configured to provide a magnetic field radially outwardly of the central axis. The monitor circuit monitors changes in the impedance of the coil, to in turn provide an indication of the amount of metal mass radially outwardly of the sensor. The monitor circuit is set to be triggered at a particular amount of metal mass, which would in turn be tailored to the particular application. In one desired application, the sensor is utilized to detect the presence of a nut in a metal plate. Metal plates as are typically utilized with vehicles will often include a number of holes which are to receive nuts. If the nuts are not received in the holes, then that particular metal plate should not be further assembled into the product. One widespread use of such a technique is with the assembly of vehicle bodies. The side sensor will detect the presence of a nut in the hole when positioned within the bore of the nut.