SAFETY FIRST: Ask an adult to help with tools you haven't used before.

Writing secret messages is easy with this cipher wheel. It scrambles the alphabet so nobody can read your message except your buddy with an identical wheel. Armies once used similar devices because they could easily change the secret code.

## WHAT YOU’LL NEED

• 2 pieces of plywood, 1/2″ x 8″ x 8″
• 1/4″ machine bolt, 1 1/2″ long
• 4 1/4″ flat washers
• 2 1/4″ nuts
• Coping saw
• Crosscut saw
• Drill
• 1/4″ drill bit
• Drawing compass
• Protractor
• Straight edge
• Dark pen

## WHAT YOU’LL DO

Step 1: Use the compass to draw a 6″ circle on one piece of wood. Draw a 7″ circle on the second piece of wood.

Step 2: With the coping saw, cut out both circles. Sand smooth.

Step 3: Use the straight edge to draw one line all the way across each disc, making sure the line goes through the center of both plywood circles.

Step 4: Center the protractor on the lines you just drew and make a mark every 12 degrees halfway around each disc.

Step 5: Draw a line through each mark, across the center of both discs.

Step 6: Staying within 1/2″ of the edge of the 7″ wheel, write this scrambled alphabet, one letter in each space: S P H I N X T O W E R C L A M J U G B D F K Q V Y Z. In the leftover spaces, write 5, 6, 7, 8. On the 6″ wheel, write the alphabet in regular order (A B C …). In the leftover spaces, write 1, 2, 3, 4.

Step 7: Drill a 1/4″ hole through the center of each disc. Assemble the cipher wheel by putting one washer on the bolt. Put the bolt and washer through the bottom of the 7″ wheel. Turn the wheel over so the letters are facing up. Put two washers on the bolt, then add the 6″ wheel. Place another washer on the bolt and two nuts hand tightened so the wheels are snug and turn smoothly.

## HOW TO USE YOUR CIPHER WHEEL

Pick any letter on the outer wheel as your key letter. Turn the inner wheel so A lines up with the key letter. Next, find the first letter of your message on the inner wheel. Look at the letter or number above it on the outer wheel. Write this down. Do the same for each letter of your message.

Example: Use the key letter R. Use the message SCOUT LAW. The enciphered message should be 7LYS8KRH. You can pick a different key letter for each message.