[sandman2234]

Since your tags on on the trailer, you will be involved in the lawsuit if they run over somebody, so think about that and then stop by the local tire store and pick up a couple of blown tires that they have removed. Mount them to a couple of spare rims and put them on the trailer. Hide the good ones. When they ask about it, tell them you don't have tires on it, since the guy you loaned it to yesterday blew two of them and brought it home like that. Offer to let them use it if they will dismount the tires, haul them to the tire store, pay for a couple new ones, then bring them home and mount them on the trailer. That much work will make them hestitant, especially if you don't tell them about the tires till they come to pick it up. Have the number to U-haul handy, and make sure U-haul has a trailer for rent actually on the lot.
I loan trailers, and borrow them, but try to return them in better shape than I picked them up in.
David from jax