Abstract: An electronic feeler gauge and a method of using the same which provides an objective means of determining the width of a gap between two surfaces. The gauge comprises a measuring element which is insertable into the gap and an indicator coupled to the measuring element for automatically indicating when the gap has been set to a predetermined distance. The measuring element comprises two plates which act as an electrical switch in an electrical circuit. When the gap gauge is inserted into a gap of predetermined width, the plates press against each other and current from a power source lights up a light emitting diode. Conversely, when the plates are inserted into a gap that is too wide, the plates do not press against each. The circuit, therefore, is not complete, and the light emitting diode does not light up. Thus, this invention provides an objective, reliable means for confirming the width of a gap. The invention can be used for gaps of different widths by varying the thicknesses of the plates.

Abstract: A trailer hitch positioning apparatus is provided for directing the driver of a vehicle that is backing up to a trailer. The apparatus includes an infrared light and sensor unit mounted on the bumper or receiver of the towing vehicle for transmitting a light beam of predetermined vertical and horizontal width toward the trailer. A reflecting device mounted under the trailer tongue returns infrared light impulses with information back to the sensors which are analyzed by a microprocessor that controls a transmitter. The transmitter audibly guides the driver's ball to the trailer hitch for coupling. A stop tone warns the driver to stop when the ball and hitch are accurately positioned for coupling.