What do you call this thing?

from old posts of folks who have used these donuts, they should be called a paint scraper/remover. too much jiggling between camper and truck.
bumpy

inner tube

Off-topic but while people-sized pass-thoughs might be de rigueur on massive expedition vehicles braving the Zulu uprisings or vast herds of rampaging ferrets, installing one can cause major problems in designing the interior layout. Plenty of people go to a lot of trouble and expense putting one in and have never used it. In a slide-on camper situation, you usually still have to deal with the rear access stairway as part of the setting up and packing procedure.

donut
bumpy

Thanks you guys...now that I have some terms I'm going to shop for it. That was a fast reply!

Pass-thru

I have heard it called a Boot.