Missouri farmer Mitchell Grainger designed and patented a Revolving Drive-Through Gate, which consists of two regular hollow-tube stock gates that are "U"-bolted to a spring-loaded, pivoting, latchable center pole. When the gate is bumped by a tractor or other vehicle, a lever on the gate releases the latch on the center pole. The unlatched gate is then pushed open by the vehicle until it has swung 90 degrees, at which point it continues to revolve by spring pressure until closed. Since there is no latching on the outer edges of the gate, the spring-loaded latch can be released from either side.