When I left the unload, I heard they were retiring the drop frames, in favor of those ones with the halfway up the side of the trailer fold-down "shelves" or flooring things to keep the packages on the lower half of the trailer from being crushed by all the stuff stacked on top.
If you don't understand what I'm saying... neither do I lol
It's like the drop frame, minus the rollers in the middle, and no drop, just flaps that fold down about halfway up from the floor to keep things from getting mushed.
One time in a drop down pup, I found under the rollers a few long steel poles/tubes loaded under that cross brace just below the rollers. I wonder what the shipping info looked like for those packages, just perpetually going here and there and no one ever figuring it out. They were there for a while lol