Western-Cullen-Hayes Wheel Crowders are special appliances designed to assist derails in unusual applications such as, location on inside rail curves and on descending grades. Wheel Crowders are mounted to the rail opposite the derail and assist the derail by guiding or "crowding" the wheels of the rolling stock, off the rail as the derail lifts and turns the wheels. Crowders are attached to the derail with a short connecting rod so they operate in unison.