I moved my bike in the back half of a giant uhaul like that. NO rings of any kind. The metal studs in the walls of the truck are kinda like C channel. You can get a hook in under a rail, and into the C channel, and it'll hold good. Since then I have gotten those little nylon strap loops that you can loop over the bars. They could be used to loop around the wooden rail too... Just an idea. Or fish the hook of the strap behind the rail and then onto itself.
