We have a Switchblade cover. It retracts like a Venetian blind. Well, you have a strap you use to pull it closed, and then pull it back open again. It goes right over the top of our king pin receiver. The fifth wheel bedroom body goes over the top of the bed frame, never touching the rails.
Here is an example:
https://tonneaucoversworld.com/p/pac...tonneau-cover/