Here's a previous thread:

[ So if I can move the tie rings, where do I place them? Must I drill new holes into the siding? What happens with the old holes, or do I just buy new rings and leave the old ones there? Can you safely fasten a tie to any of the ribbing? I had a friend who had a horse pull back and take the tie ring with them, it came from the manufacturer constructed poorly.

It's easier to leave the presently installed tie rings in place. New rings are usually less than ~$5, plus the cost of some stainless hardware. You can usually place a new tie ring wherever there is a structural wall stud. Holes will have to be drilled completely through the center of the stud and wall, using a new tie ring as a template for the hole spacing.

The bolts will have a countersunk head against the ring. On the inside of the trailer, you'll want to secure the bolt, using a large fender washer and a self locking nut. Cut the exposed tail of the bolt flush with the nut, and file or sand the rough edges smooth.

Here's one source of rings:

http://www.horsetraileraccessorystore.com/drings_tie_loops.htm

Gard