Wing-Open Truck & Trailer Parts Truck Body Fittings supplies wing-open truck body parts (gas springs, hydraulic power packs, oil cylinders, toggle fasteners) and trailer parts: couplers, towing balls, jockey wheels and trailer jacks. Complete hardware for wing-open vans and towing applications, in galvanized and painted finishes. Applications: wing-open trucks, box trailers, towing & caravan. Need a quote? [Contact us] with your part name and quantity.