The stabilizer wheel locks that wedge between the tires of twin axle
trailers will keep the trailer from shifting from wind but I wouldn't
trust them to hold on a steep hill. I know from personal experience that
they will not prevent the trailer from being towed away as I had a memory
lapse and did just that. The locks were thrown out from between the tires
and both had their pull screws bent or broken.
There are locking chocks that clamp onto the tires of single axle
trailers so that they won't slip out of place from wind, but they don't
look any more secure against towing than my locks.
The clamp-ons will keep the wheel from turning. The ones I've seen
advertised for trailer use will only work with non-braked wheels, though.
The ones some traffic and parking departments will work on braked wheels,
obviously, as they are used on parked cars. I suppose they are expensive,
though.
Al