When I saw the cryptex Instructable (https://www.instructables.com/id/How-To-Make-a-Cryptex/) I thought: "I will make something like that with my grandson this summer to generate coded messages". He is smart with his hands and he will love building one. I also realized that if we were to play spies, I should have my own... I did not want to have one that he could compare with his, so I decided to make something quite different. Since I have some experience with sliding rules I decided that my machine would be flat.

Step 1: You Only Need

- a piece of cardboard, about 2.5 or 3mm thick and 10x20cm large
- glue
- a sharp cutter knife (and a rule!)
- the template (flatcryptex.pdf)

flatcryptex.pdf
Download

Step 2: Prepare the Base Material

- Download the template
- Print the template
- Paste the template on the cardboard sheet
- LET DRY (over night, to be sure!)
- As you can read on the template at this step, you will have 3 layers (bottom, middle, top)
- Crop, but do not harm yourself with the knife

flatcryptex.pdf
Download

Step 3: Separate the Pieces

When you're sure it is really dried, separate the pieces by cutting along the horizontal black lines. Be careful: the cardboard is thick, so do not make any false move that might harm your fingers!

Step 4: Add the Middle Layer Guides

Put some glue on the bottom layer pink zones and paste the guides from the middle layer. Check that the central piece from the middle layer can slide easily between the guides.

Let dry (one hour should be enough this time).

Step 5: Add the Top Guides

Put some glue on the middle guides pink zones and paste the top guides. Once again be sure the central top piece can slide easily between them.

Let dry (you knew that, didn't you?)

Step 6: Fix the Central Part of the Rule

Put some glue on the pink zone of the middle central part and paste the top central part on it. Dit I say "Let dry"?

OK, this is only a fast done object for my summer vacation with my grand kids. If you have time, do the same with some nice wood (or aluminum). Print, paint, or engrave. I would be interested in seeing pictures of your results.

Step 7: How to Use It

I am sure you know exactly how to use it, but I must be complete...

Such a coding machine is designed to use a Caesar's code encryption, which is an alphabet shifting. So let's say you want to use a +6 shift. As shown on the picture, C will become I. Or, talking about my name:

"PAPYDOM" would be encrypted into "VGVQJUE"

Pro: fits in my pocket
Con: you can not read a whole word, as with a cylindrical cryptex. You must read letter by letter!