Did you ever have a club house where you had to have a secret password or knock to get in? While we can’t exactly fit into the old tree house, that doesn’t mean we can’t still keep the secret knock between friends. The only difference is that you have to be a bit sneakier in the implementation, or not everyone will play along.
The Secret Knock Detecting Lock is a DIY project that is more for fun than actual security. It’s not for beginners, but the idea is hilarious, and could be used for a room or cabinet that you only want some people getting in to. You will need knowledge of microcontrollers, basic soldering, be able to read a basic schematic. The tools and parts are pretty easy to come by aside from that. You can decide what to use it on, and can change the lock combination whenever you choose. Just make sure this isn’t the only way to get into your house, as a burglar would only need to listen to the pattern once to be able to break in.