Make a Spy Decoder

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Turn your Scouts into spies and challenge them to crack a secret code


Thin card
Coloured pencils
Split pin paper fasteners
Marker pen


1. For each decoder, ask the Scouts to use the compass to draw three circles 8cm, 6cm and 4cm in diameter (measuring 4cm, 3cm and 2cm on the compass) and cut them out.

2. Now colour each of the circles in using different coloured pencils.

3. Take the largest circle and make small marks 0.9cm apart around the outside edge using a pencil. The object is to create 27 sections. For decoders to be compatible, they have to have the same number of sections.

4. Ask the Scouts to punch a hole through the centre of the largest and middle circles. Attach the two circles with a split pin paper fastener and then draw the 27 sections on the middle circle, using the lines from the larger circle as a guide.

5. Ask Scouts to write the alphabet in capital letters in each of the sections on the largest circle, putting a question mark in the final, 27th section. Now ask them to do the same on the middle circle.

6. Attach the smallest circle to the centre of your decoder.

7. Now create a code by lining up letters on both circles (eg. A + Z).
To write a coded message, find the letter you want on the larger circle and write down the corresponding letter on the middle circle.

8. To crack the code, find the letter on the middle circle and write down the corresponding letter from the outside circle.



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