I can't send you a PM as you have them turned off. So here: Send me your email address and I will send the other pictures that I took before the client took the truck back. The pictures barely show the screws that hold it together. The rails behind the cab have one stainless screw in the center of each going into the front posts. I also installed two stainless screw-in studs in the side rails and matching alignment holes in the end of the front rails on both sides of the bed. To remove the owner would need to unscrew the center screws, and have a helper help him lift the whole unit out of the stake pockets. The front rails would come off easily when the sides were moved apart, taking it off of the studs.
When I finally get my truck done, I am going to make some for it probably the same way except out of Accoya instead of Oak.