How to secure a toilet
This is the lock on the toilet door. It requires a four digit combination to get in, but it has been set up slightly wrong so that any combination of the four correct digits will open the lock. At first thought this seems like a bit of a security flaw as it decreases the chances of guessing the correct combination, but hey, it’s just a toilet, and actually it’s makes getting in easier as you only need to remember the four digits, not the order they go in too.
It makes me wonder if a similar approach could be used in securing other systems, so that the information that is used to get access doesn’t need to be 100% accurate but has a margin of error to allow for the user to make a mistake.