Spies are everywhere, it seems, from movie screens to books to current news headlines. It is no surprise that playing at spies is a childhood favourite, in part because of the variety of fun gadgets that can be used in such games. Everyone loves a good secret, and with this simple homemade spy gadget that can be constructed out of paper, children can share encoded messages with their friends for hours of constructive entertainment.
Cut two strips of plain paper about 1 inch wide and 8 1/2 inches long.
Create a random pattern of holes along the centre of the paper strips, using the hole punch. The holes should not overlap or be evenly spaced and should be identical on both strips. This is your code strip.
Lay one of the strips with holes over a piece of paper, lining it up cleanly against the left edge of the paper. Use it to encode your message: one letter per hole, until your message is complete. If your message is longer than the number of holes, move the strip down a line and continue, making sure to always use the same side of the strip.
Fill in the spaces between your message with letters and numbers. Give your partner the other code strip so they can decode the message.
For more privacy, you can write your messages in invisible ink: Use a cotton swab and lemon juice to write the message and let it dry. Your partner needs to heat the paper using a hair dryer or other gentle heat source to cause the "ink" to appear.