Also known as the Domino Code. The code is quite simple, although it looks complex.
Draw a 3 x 3 naughts and crosses (tic tac toe) grid with the alphabet arranged in the squares as shown in the title image.
To encipher a message each letter of the alphabet is encoded by indicting the type box that it is in and a way of indicating its position.
E.g. the letter ‘f’ = or or
Easy! Can you decipher the message intercepted by Agent Kat above?
If you want, you can make it harder to solve by combining it using something like the Caesar cipher.