mtaxter, from your other post I believe you own a 233s as I do. This appears to be a the height adjustment for how the slide pulls onto the outside of camper. Looking under you'll find two bolts on either side of this bolt. It looks as those 2 would be loosened and the big bolt you are talking about would be be adjusted, then the outside bolts re-tightened. This would align the seal when the slide pulls tight. Just what I see though. Something I wouldn't mess with though unless there's a problem, and then I'd contact your dealer first. Anyway, although long, it should be as is. I got the same, just books odd.
Doug '71 n Deb 'better not'
DS1 '98 DS2 '99 DD '04
2000 Coleman Utah, since '05 replaced with
2011 Rockwood Roo 233s
2002 F150 FX4 SuperCab