Position the refrigerator box so it is standing length ways, and the opened side is facing the floor. Choose one side to be the "stage area," where the puppets will be seen by the audience, and cut a hole in that side of the box using the box cutting knife. Ensure the hole is at the top half of the box with a margin of at least a few inches from the edge of the box for support. The size of the hole depends on how big you wish the stage area to be.
Make an entrance for the puppet masters on the opposite side of the box, which is the side facing the stage area. Cut out this side of the box, but again leave at least a few inches at the top for support. This will be the entrance for the puppet master.
Paint the front of the box. If there are logos from the refrigerator, paint a thick layer of white paint to hide the box's origin. When the white paint dries, it's time for the kids to get creative and paint a border around the puppet stage and other pictures below the hole.
Attach the dowel rod to the inside of the puppet stage, with the curtain material already over the rod. Strong gaffer tape should hold the rod and curtain and is a safe and easy solution.
Choose a spot for the puppet show to happen, and use the gaffer tape to fix the flaps of the box to the ground to give it support.