of Wellville. Today's fifth wheels allow the trailers to slide into the fifth wheel and lock into it, and are a very reliable unit when maintained and serviced properly. The engagement of the king pin into the fifth-wheel locking mechanism is the only means of connection between tractor and trailer; no other device or safety mechanism is used. Couplers and pintle hooks use safety chains in the event of a trailer separation while going down the road. Trailer-to-trailer connection can also be made by using fifth wheels. See also Drawbar (haulage) Fifth Wheel and Gooseneck Ringfeder Tow hitch Tractor unit References General Bill Johnson, The American Truck Historical Society Darlene Norman, The Fruehauf Trailer Historical Society Trucks