A converter dolly allows a vehicle equipped for commercial towing to accept a fifth-wheel trailer. It has a full axle and helps balance the weight of the load and the trailer on the towing vehicle.
Fifth-wheel trailers typically attach over the bed of the towing vehicle, so a converter dolly must be used for nonstandard applications. A trailer is any wheeled vehicle that provides no power of its own. It must be connected to another motorized vehicle to be moved. A fifth wheel is a coupling device that allows a trailer to be securely connected to a towing vehicle while having free horizontal movement.