Installing hitch safety chains takes a few extra minutes when you're preparing for a road trip with your trailer, but they'll be well worth it to keep your towing equipment safe. Whether you decide to use cables or chains, make sure they can support whatever you're towing. On many Web sites that sell towing accessories, you will see listings for "Class II" or "Class IV" chains. This refers to the weight of your trailer [source: Trailer Hitches]. In short, don't get hitch safety chains too weak to hold whatever you're towing. The sizes of the chains you get also depend on your towing vehicle. Most light duty trucks will use 5/16-inch thick chains. Most medium-duty trucks use half-inch chains, and heavy-duty vehicles handle 5/8-inch chains [source: AW Direct].
Here's how to install them:
Have two chains crisscrossing under the trailer tongue connecting the trailer to the bumper or the receiver on your towing vehicle. Attachment devices (like trailer hooks) at the end of the chains should be sturdy and solidly in place [source: Lamm]. If the chains are too long, they can be twisted until they're short enough. Also, wires should be used at the hook points to keep the chains from accidentally falling off. Make sure you then attach the chains to the towing vehicle itself and not to another part of the trailer hitch. This ensures that the two units will be kept together if the coupler separates from your receiver unit. Crossing the chains under the tongue will allow them to form a net that catches the trailer's tongue in case it breaks loose and falls to the roadway.
The chains must be small enough to keep the trailer from drifting but with enough slack to allow the towing vehicle to turn with ease. They also shouldn't be allowed to drag on the ground.
For more information on hitch safety chains and proper towing techniques, please see the links on the following page.