When I first saw these Bolt programmable padlocks, I assumed they had some sort of fragile optical electronics inside that memorized whatever key you inserted and used that to match during unlocking later. I wasn’t wild about that, for both cost and security reasons.
I was wrong – the lock is entirely mechanical and subtly brilliant. The first time you insert a key and turn it, you’re actually locking in what is in essence a programmable tumbler plug. It’s hard to explain – I suggest you watch the animation on the How it Works page.