While out walking in the New Forest, I came across a gate which held multiple locks in series.
Initially, I pondered why one would set up such a peculiar arrangement. Did someone lose the key to the crusty old rusty lock, so they added another newer one? Why wouldn’t they dispose of the chain and replace it with a new one?
Leaving this, admittedly insignificant thing, behind me, I promptly forgot about it for many weeks.
Then, while out walking the dogs, I passed by a block of flats, and what would catch my eye, but a gate locked with multiple locks in series. One forgotten rusty lock I could explain away, but this was something people were doing intentionally.
Well, I asked around and found out that it is intentional. And it is far cleverer than I could dream up.
If you told me that I needed to lock up a gate for a block of flats, but every person in the flat needed to be able to unlock it, I would naturally say “Use a combination lock, and then tell everyone the number!”
But combination locks are easy to ‘brute force’ you would say.
“Use a padlock and give everyone in the flat a key!” would be a very reasonable and practical response to this.
However, what if someone loses a key? Now you have to replace all the keys with a group of people who don’t all keep the same hours; making handing out the keys a nightmare.
What if you are the New Forest Park Authority, and you want your key to open any of the gates in the New Forest, but you don’t trust others to give them access to every gate, only specific ones?
Well, at this point I would be stumped. I actually think it would have taken me a long time to think of this solution (which is why I’m so impressed).
Let each person attach their own lock, chained in series, into one long lock. When someone unlocks this ‘chain of locks’, they only need their own key. Need to add someone? Add another lock!
This is so simple, yet so clever. And now you know about it too!
