Travel trailer security - keep it or stuff from being stolen

Even with a hitch lock, a thief can readily use your trailer's own safety chains - wrap them around the truck hitch and tow away for a short distance.

If I am going to be gone from campsite for awhile, I park my truck in front of the trailer which would make it difficult to tow away.

As pointed out, locking doors and closing windows is only going to stop a child from getting into your trailer.