How to build a one-piece
folding picnic table out of 2x4 lumber
Step 9. Prepare for the seat boards
Prepare the side-frames to take the seat boards.
Fold the side-frames over (into seat mode) until the tops of the horizontal seat members [e], [f], and [h] are flush (even), place a piece of
cardboard packer between pieces [f] and [h] and then apply a clamp to each side frame to hold it in that position.
Then place the side-frames apart and parallel in readiness for the seat boards.
You might have to place a little packer under front legs [a] to balance the frames.
The cardboard spreads pieces [f] and [h] apart a little bit to help ensure the frame doesn't bind during the folding motion.