What you need
The printed template
Card or thick paper
Scissors
A split pin, or a drawing pin and a rubber
How to build it
Print and stickPrint the template, glue it onto card, and let it dry flat.
Cut out both circlesThe big one and the small one. Take your time on the edges.
Pin them togetherThrough the middle, so the small circle spins freely inside the big one.
Choose a shiftTurn the inner circle until A on the outside sits above your chosen letter.
Read your message offFind each letter on the outer ring and write down what sits underneath it.
Tell your friend the shiftOne number, and they can turn their wheel to match.
Cut the small circle a little inside the line rather than outside it. If it is a hair too big it will jam.
The template
Print this at 100 per cent, not fit to page, or the sizes will be wrong. The ruler line below tells you whether it printed correctly.
The bar above should measure exactly 10 centimetres. If it does not, your printer has shrunk the page.
Now send something
Set the wheel so A sits above D, then write THE DOG ATE MY HOMEWORK. That is a shift of three, which is exactly what Caesar used.
The shift cipherBack to Make