I use a pair of locks and a 12" piece of chain to keep our Casita
in her nest. The locks are large enough that they will not pass thru the spokes on the wheels and there is a hole in the mount of the axle
that the other end is locked to.
If you use a long enough chain you could get away with only one lock or two if you wanted to chain each wheel.
OBTW, even this will not stop a determined thief!