How to build a one-piece
folding picnic table out of 2x4 lumber

Step 14. Stop the table from spreading

We need a spread-stop (for lack of another term). Otherwise the table will just keep spreading out until it is on the floor.

O.K. Open up the picnic table until the from leg and back leg are 47-1/4" (1200mm) apart overall.
Find two pieces of wood (or something) slightly longer than 47-1/4" (1200mm) and clamp them to the bottom of the front and back legs, one each side of the picnic table. That will hold the table in position and stop it spreading while you fix the spread-stops.

Apply two spread-stops each end. Spread-stop 1 and Spread-stop 2.

Spread-stop 1 is piece (g1). There are two, one each end. Fix them (g1) to the ends of the tabletop rails (g) so they are positioned flush with the ends of the tabletop rails (g) and against the front legs (a). Fix with glue and screws.

Spread-stop 2 are angle brackets (sliding door stopper type brackets). Fit them to the front legs (a) as close to the outside of the leg as possible and hard up against the end underside of the tabletop rail (g). Ensure it is as close to the outside of the leg as possible otherwise it could be in the way when folding the table back to bench mode.