Could someone describe the construction of truck campers and travel trailers?

particularly the frame. it's just 2x2s right?|||This is a very broad subject, but yes, most are made with 2x2 construction. There are variations to this and research on a particular model you may be interested in is necessary. Have you ever seen the aftermath of a rollover of one of these vehicles? On the other hand, I have owned a motorhome built in '72 that had all steel framing. I didn't roll it though. Newer units will have some vapor barrier and be reasonably well insulated with possibly fiberglass construction.|||fiberglass?