I'm thinking from what Reaper said is the paths taken in the game mean they only unlock if you take that path to the endings or it is already unlocked when you play it?
Locking = When you hear the *click sound when you push the thing up, you then press the hold key to lock the pin in place and continue on with the remainder pins. If you didn't know that yet :P
We waited a lot to make that choice useful u.u