First, you need a big piece of cardboard, tape, scissors and two small mirrors. Make a tall box out of the cardboard, making sure that the top and bottom are about the size of the mirrors. Next, cut a flap on opposite sides of the box, making the flaps the same height as the mirror. Then tape the mirror to the inside of each flap and cut away the opposite side. Bend the flaps at about a 30 degree angle, so what is reflected out of the top can be seen in the bottom. Finally, tape the seams, recheck the angle, and now you have a periscope!