In Dan Brown's novels a Cryptex is a device that contains a hidden message. Rotating dials must be aligned to unlock the device. This homemade, cryptex-inspired clue uses two card tubes to hide the clue. The tubes have to be correctly aligned to read the right answer.
1) Find or make two tubes, with one just a bit smaller to allow it to slide into the other. If using toilet roll tubes you can cut one down its length and tape it back up to make it narrower than the other. Ideally the smaller one should just fit tightly into the larger one.
2) Work out how many letters there are in your clue; clues of around 8 letters work well. Randomly cut a hole for each letter into the bigger tube, along the tube's length. For example, maybe measure 1 centimeter down the tube and cut a hole. Then move another centimeter or two down the tube, rotate the tube a random amount and cut a new hole in a position that is not right next to the first hole. Continue moving down the tube until you have cut a hole for each letter.
3) Slide the smaller tube into the larger tube. Carefully write your clue onto the smaller tube through the holes on the bigger tube. Do not twist the tubes - keep them aligned.
4) Now rotate the inner tube to hide the letters, and then carefully write new, random letters though the holes onto the bigger tube. Repeat this a couple of times (you can skip any holes if you have revealed a letter in one of them when you rotated it).
5) Hunters must be given the tubes and be told to rotate them to reveal the clue. They will have to rotate them, read the letters and keep rotating until they find the alignment that reveals the clue.
6)For a harder clue, make multiple versions of the smaller, inner tube, each with random letters that align to the holes. The hunters will have to try each tube, rotating each one, until they find the right one that reveals the clue.