A towbar can refer to several different types of vehicle towing devices. There are two towbar varieties that are most common: a triangular shaped system of bars that attaches to the rear of one motor vehicle and to the front of a second vehicle, so that the first vehicle can tow the second; and a tow hitch system that attaches to the rear of a vehicle in order to tow a trailer or a variety of other applications.
A towbar designed to tow a second vehicle can be bolted to the tow vehicle--called a coach-mounted system--or it can be bolted to the front end of the vehicle being towed--called a car-mounted system. In either case, the towbar connects the towing vehicle to the vehicle being towed, and it allows for swiveling between the two vehicles so that they can move independently in turns and over bumps. A towbar must be connected in a redundant fashion. In other words, there is a primary connection which is typically a ball and socket system, and there are safeguards, usually in the form of towing chains that connect the towbar to the towing vehicle or the vehicle being towed.
The other type of towbar is more commonly known as a tow hitch or receiver. It is a steel bar that is bolted or welded to the frame of a towing vehicle, with a square hole meant to receive a draw bar attached to a ball hitch. The tow hitch and the draw bar are separate components and are interchangeable; therefore, the tow hitch can receive any draw bar designed for a variety of purposes, provided that the bar and hitch are the same size. For towing, a two inch (5 cm) receiver and bar system is most common, though an inch and a quarter (3.175 cm) system is available, too. The smaller tow hitch system should only be used for small trailers or other purposes, such as bicycle racks or storage racks.
Both the towbar and the tow hitch designs require special wiring to ensure that the trailer or vehicle being towed has appropriate brake lights that work in conjunction with the tow vehicle. This is accomplished by wiring a female-end harness on the towing vehicle to a male-end harness on the trailer or the vehicle being towed. This wiring is necessary to make the trailing vehicle or trailer street legal. In addition, safety chains should always be used in conjunction with the primary connection point.