This metal detector rental can be used for ferrous metals only (ferrous is an adjective used to indicate the presence of iron). When a magnetic disturbance, such as a metal fence, is confronted, simply press the "erase" button and the disturbance is erased for continued searching without interference. There is no need to reduce the sensitivity, the Magna-Trak 102 metal detector always returns to perfect magnetic balance when the "erase" button is pressed. The Magna-Trak 102's LCD indicator offers a digital bar graph display, in addition to a standard audio tone, to precisely identify the target object, especially in noisy, congested areas.