agree with scoop, keep them insured, anything you do is simply a deterrent, and better than nothing, if they want it bad enough, they will take the truck, trailer, sxs and be gone
I've backed the utility trailer in against a wall, parked under the canopy entrance at hotels overnite, etc.
we have had a couple in the area ripped off while owners away from machines and out hunting, whoever pulled up threw it in neutral and towed it away never to be seen again
if im out hunting and going to be away from it, trail cam is pointing at it, pull the steering wheel\throw in backpack, take the key and hope I don't have to make a pickup call when I get back