Using two padlocks, pieces of cardboard are locked together, and must be unlocked to solve the clue. This works best with corrugated card, as it is thicker. Write the clue on the card and sandwich the pieces together. The hunters must use other clues to find keys, which then can unlock the card allowing them to get at the clue.
In this example the pieces of card have to be unlocked so that they can be put together in the correct order. By following the line from start to end the letters spell out a local village "Thurlaston", which is part of another clue.