How to Make a Booster Seat for a Picnic Table

First, cut your 1×10 to two 14 inch pieces. Then, measure 7 ½ inches and 9 ½ inches from the bottom of your 1x10s, and 7 inches across like this:
Do this to both 1x10s, then cut out the 7×2-inch sections with your jigsaw and save the nicest, most intact piece to use later as the brace. A tip before sawing: put holes in the corners with a large drill bit to make it easier to turn the saw blade. If your notches come out looking a little raggedy, don’t worry. As long as it can slide onto the bench, it doesn’t really mater what it looks like.

Line up the bottom of your 1x10s like this and measure the center.  Attach the door hinge with the screws included.

Now your booster seat should fold together pretty evenly. If you need to adjust it, now is the time.  Mine was a smidge off and it didn’t affect the look or functionality.  Fold it to the closed position and measure even increments to drill holes for the seat. I made 7 holes 1-1/4″ apart, but it depends on the size of rope you use and the size of the drill bit.  Drill through both at the same time.

Open the seat to the desired width and thread the rope back and forth.  Tie off at the entry and exit point. I used a match to melt the knots, but make sure to check your rope material for flammability if you’re going to do the same.

Your seat is almost done! Slide it onto a chair or a bench and open it to the seated position. Measure the width between the two sides where the top of the notches meet the picnic table bench (or chair if that is what you are using right now*).
Take the piece that you saved when you cut out the notches and trim it down to the width you just measured (if your pieces are destroyed, just cut a new one 2 inches by what ever distance you measured).  This is the brace that will snap in right above the bench surface to keep the booster seat from closing together.  It should be snug, but not too difficult to pull in and out.  I drilled a hole through the brace and use a carabiner to attach it to the seat while not in use. Otherwise, I’m sure I’d lose it or forget to bring it with me. And without the brace, the booster seat doesn’t work.

Sand the wood and paint if you want, then go have a picnic!

*This is intended to fit a standard picnic bench, which measures 1-3/4″ thick.  Do not use this on dining chairs or anything that is thiner than a picnic table because it will not be as sturdy.