Here's what I currently use and have available depending upon the situation.
Locks:
Trimax UMAX100 Universal 'Die-Cast' Dual Purpose Coupler Lock
with a lock pin bar that goes through the latch lever
Also, I have, but don't use much but will when I move it to outside storage (due to new buggy).. and fits just fine.
Trimax TWL100 Ultra-Max Adjustable Wheel Lock
and finally, when I did have to store outside in my, then, apartment lot parking with CampInn cover, I used what I call "Land Anchors", from the idea of a sea anchor.
Five huge, apx 40lbs each?, cinder blocks, the ones with the 2 holes in it, usually for walls.
With 4 heavy chains and locks. I then would put 2 blocks next to front latch, one on each side under the trailer and one in the back center under trailer.
I'd chain up the front around the frame, through the holes in the blocks and back to 'Grandmas House". hehh and lock with good round storage padlocks.
The two side blocks, I chain the axle with the heavy chains and then coated cable locks wrapped around the door latches so it can slide off and back underneath to the frame.
Back, again chained to the axle or frame, fergit, and a coated cable lock wrapped around the back hatch.
It worked. Took about 5 min to lock it all up, kept the blocks under the trailer so I didn't have to move them and could back right in over them.
I'll be using the same type of senario when i move it to the Storage place just to be sure.
Hope that helps.
Knowing fully well, if they want it bad enough they'll get it, but not without a fight.. heheh, Krap, just moving those heavy blocks is a PITA, but once moved and set, done... I just relocked the chains around the blocks when gone...
HTH...