Thor uses these "bags" to go around plumbing and wiring for the slides. As the slide moves the plumbing and wiring stay in place so the bag runs back and forth around it.
Unfortunately many times these bags do not seal well and there are large gaps where bugs, etc. can get into the coach.
I actually had my wife make some fabric panels with velcro sewed into them. I then attached some velcro to the bottom of the slide around the openings for the rollers, plumbing and electrical. When I have the slide out I attach the panels to cover the openings under the slide to keep bigs and critters out.
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