Now construct your washer box. Put the wood pieces on the piece of plywood and glue them using Liquid Nails. Then you should add strength to the box by putting nails into the bottom. Do this twice to make two boxes.
Now all you need to do is screw the cans in the center of the box. Make sure that the cans are 3in wide and 6in tall. Drill a hole in one side of each box and run the rope through the holes, knotting it on the inside of the box.
Now you will have an awesome summer game to play in your back yard.