A Fast and Flat Coding Machine




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)

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

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!

Participated in the
Pocket-Sized Contest



    • Growing Beyond Earth Maker Contest

      Growing Beyond Earth Maker Contest
    • Backyard Contest

      Backyard Contest
    • 1 Hour Challenge

      1 Hour Challenge

    63 Discussions


    4 years ago

    This 'ible is so cool. I will be making loads more of these. The idea is great ???


    7 years ago on Introduction

    im gonna make one from 3mm (1/8in) aluminium and rivet the pieces together, using glue only to affix the labels.

    3 replies

    Reply 7 years ago on Introduction

    oh sorry, i forgot about my project idea and this page until now. this next month ill be able to get the materials, including the pop rivets. heh....i still have teh pdf.


    Reply 7 years ago on Introduction

    of course ill need to make a top/bottom margin space for the rivets, but that'll be easy peasy for me.


    7 years ago on Introduction

    cool but is it ok to use corregated card for it instead of solid


    7 years ago on Introduction

    Wow. This is pure genius. I remember this is the 'ible that made me decide to join this community. I've forgotten about it until now. I'm making it as i speak. I'll post a pic when im done!

    3 replies

    Reply 7 years ago on Introduction

    I saw it on your page. Well done! Maybe you put a little bit too much glue, but it was the same for me the first time I made a book cover. I was not used to glue on cardboard and I had to start again from the beginning. But if your rule can slide, it's just great. Keep on making/building/hacking, it's so fun!

    Hey! I forgot about this project a long time ago... Maybe I'll make it sometime this break. I'm gonna make it out of my failed math project (by failed I meant the second version which I didn't use).


    9 years ago on Introduction

    My family an I love the design. So far I've made two out of cardboard (one for my father and one for my brother) and I'm working on a third out of balsa wood to aid in the sliding between the pieces Thank you for you great ideas!

    2 replies

    9 years ago on Introduction

    The Cryptex is completely different but good job!