Assuming that you have a single axle tent top trailer, looping a piece of chain through a hole in one wheel rim then around the axle/spring then connect both ends with a padlock. For a dual axle trailer chain both wheels on the same side together.
If you are concerned about a bolt cutter cutting the chain, heat treated chain is available at most home inprovement centers/hardware stores.
Remember that most thief protection devices are of a delaying nature, when seconds/minutes count, thieves won't spend a lot of time when stealing something.
1998.5 Dodge, 24V, auto, 3.54, 2wd. BD Exh. brake. CB, Prodigy Brake Controller, Aero 60 gal. tank. 200,000 miles
1998 Hitchhiker II, mod#31RLBGBW, RBW L'tl Rocker Hitch, Generac NP50 G generator. Dexter EZ lube 7,000# axles with 8,000# capacity brakes