Trailer security
On the side doors of my enclosed trailers, I had the double-lock flush mounted latches with the tractor trailer swing arm locks, or whatever they are called, over the top of them with a HD padlock.
Rear ramp doors always had a lock/latch assembly on each side.
Tongue was also doubles with a ball-type lock and another HP padlock through the ball latch. All padlocks were keyed alike.
Sometimes I padlocked chains through the wheels also.
I hadn't gotten around to the other good suggestions that were mentioned.