Most projects we feature are of the metal/wire/wood variety, but there is an entire community devoting to making very interesting and intricate things out of paper. Imgur user [Criand] has been hard at work on his own project made entirely out of paper, a combination lock that can hold a secret message (reddit post).
The motivation for the project was as a present for a significant other, wherein a message is hidden within a cryptex-like device and secured with a combination that is of significance to both of them. This is similar to how a combination bike lock works as well, where a series of tumblers lines up to allow a notched shaft to pass through. The only difference here is that the tiny parts that make up the lock are made out of paper instead of steel.
This project could also be used to gain a greater understanding of lock design and locksport, if you’ve ever been curious as to how this particular type of lock works, although this particular one could easily be defeated by a pair of scissors (but it could easily cover rock). If papercraft is more of your style though, we’ve also seen entire gyroscopes and strandbeests made of paper!