Thanks to all of you for your replies!
Yes, it is a stick frame without ply attached yet and it is warped in the up and down direction, not side-to-side. It is not the chassis or the deck. It is the stick frame that is warped. When I lay it down on the deck, (which is where I built it - straight - before it warped) I can see that the last 52 of the 100 inch bottom board are warped and pushing everything out of place. This means that when I set it upright, as if I were going to attach it to the deck, the whole back end of the wall has it's behind up in the air.
Last night, I experimented by unscrewing the bottom board from the upright boards. Then, I wedged boards between the uprights and the bottom board: a 1-1/2" piece of wood at the end; a 3/4” piece of wood about half-way through the warp, and a 1/2" wedge a little further along.
This morning, I pulled the wedges out and, yes, the board was back straight. So, I think you're right. It’ll be okay and will stay straight, once it's glued and screwed in place.
PS. I'm using Poplar for my frame, which is a very light weight, blemish-free, reasonably strong wood that is usually used in cabinet making. Even though I try to wait at least a week after purchase before I use it, this wood is usually dry and stable. I live very close (between) to two tributaries and a large river and I suspect that it warped because I allowed it to sit on the floor and it probably absorbed moisture through the garage's cement floor (no moisture barrier). Because we're in a drought situation, I thought it would be okay...I've decided I was wrong about that. Thanks again for all your help.
