I am a drag racer and have a very costly car and lots of expensive parts and tools in my trailer. The freeking thieves have stopped stealing trailers, they are taking the whole rig. All the above suggestions are good, but you better have a GPS on your rig. I tow with a diesel truck and I remove about 3 relays from my fuse box, chain the trailer to the truck, try to park it where it can bee seen by security if there is any, and chain and lock the trailer wheels together wrapped around the axle. So far I have been ok, but I know several people that have lost lots of money. My suggestion is you almost can't do enough. Nothing is overkill these days.