Did you hear about the little orphan girl who found a pocket knife? Cute kid, red hair, freckles... smart one, too. She didn't want to cut things or carve things, so she started working on the blade instead. She wore it down and shaped it, until she could use it for what she really wanted: picking locks. She wanted to be able to escape the orphanage with it. And she did.
They brought her back, of course. They didn't find the knife, though, so they didn't know how she'd escaped until she did it again. This time, they brought her back and changed all the locks. It didn't help; she picked the new locks, too. So they replaced them with more and more complicated locks, mechanisms that were harder and harder to pick. It didn't make any difference, though, because she never figured out her secret.
It was a hard locks knife for her.