Dowsing is the detection, usually with a divining rod, of hidden (usually underground) resources of water, metals, etc. Another frequently used technique employs a pendulum held in the dowser's hand; the direction and magnitude of swing provides information as to the material beneath the ground. Laboratory tests have shed little light on dowsing, though some dowsers have remarkable records of success. According to one theory, the perception of magnetic fields may be involved (see dowsing and a possible magnetic sense).