Parts of a Trailer Hitch – Receiver, Ball Mount and Coupler

All 8 parts on the diagram

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Start here: 5 main parts 5

Receiver tube The square tube fixed to the vehicle's frame. Its rear-facing opening takes the ball mount or other accessories. 1¼ inch for Class I and II, 2 inch for Class III and IV in the US.
Ball mount (drawbar) A square bar that fits into the receiver and carries the ball. It comes with a rise or a drop so the trailer tows level.
Hitch ball The trailer's coupler fits over it. Its shank bolts it to the ball mount.
Coupler The socket at the front of the trailer tongue. It fits over the ball, making a ball-and-socket joint that lets the trailer turn.
Trailer tongue The beam at the front of the trailer that carries the coupler.

On the trailer 3

Tongue jack Lifts the trailer to the height of the ball. A jack at the tongue, for hitching and unhitching.
Safety chains Chains from the trailer to the tow vehicle. They hold the trailer if the coupler comes apart on the road.
Electrical connector The cord and plug connecting the trailer's lights to the tow vehicle.

How this list was compiled: Read 2026-09-27. (1) Wikipedia, Tow hitch, https://en.wikipedia.org/wiki/Tow_hitch : receiver-type hitches with a rearward-facing opening that takes removable accessories such as ball mounts; the ball mount a square bar that fits the receiver, with a rise or drop for level towing; the hitch ball attached to the ball mount by its bolt or shank; the trailer tongue or coupling slips over the ball; US receiver tubes of 1¼ inch for Class I and II and 2 inches for Class III and IV; the vehicle must be electrically connected to the trailer. (2) Wikipedia, Trailer (vehicle), https://en.wikipedia.org/wiki/Trailer_(vehicle) : the trailer coupler fits on the trailer ball, a ball-and-socket joint that allows relative movement; trailer jacks lift the trailer to hitch or unhitch it, and some trailers have one built in at the tongue; electrical feeds for the trailer's lights. (3) Wikipedia, Fifth-wheel coupling, https://en.wikipedia.org/wiki/Fifth-wheel_coupling : couplers use safety chains in case of a trailer separation on the road. Licence: own work

The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work

How it works

The parts of a receiver trailer hitch and the front of the trailer it pulls, drawn as the jack lowers the coupler onto the ball. Start with the 5 main parts, then the vehicle's side and the trailer's.

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On the tow vehicle

The receiver tube is fixed under the bumper. The ball mount slides into it, with a rise or drop so the trailer tows level, and the hitch ball is bolted to the ball mount.

On the trailer

The coupler at the front of the trailer tongue fits over the ball, a ball-and-socket joint that lets the trailer turn. The tongue jack lifts it on and off the ball. Safety chains and the lights' cord go back to the vehicle.

The ball mount must match the hitch's class: in the US a Class III or IV receiver takes a 2-inch bar, Class I or II a 1¼-inch one.

Questions and answers

What are the main parts of a trailer hitch?

On the vehicle, the receiver tube, the ball mount and the hitch ball. On the trailer, the coupler at the front of the tongue, which fits over the ball.

What is the part that slides into the hitch receiver called?

The ball mount, or drawbar: a square bar that fits the receiver and carries the hitch ball, with a rise or drop to keep the trailer level.

What are the chains on a trailer hitch for?

They are safety chains: they hold the trailer to the tow vehicle if the coupler comes off the ball on the road.