How do you create a new key using just a lock?

Question

Locksmiths do it all the time, or at least I think they do.

Answer 1

That's right, it's tedious to do by hand yourself though.

Locksmiths have a machine to do the hard work.

First you'd have to remove the lock cylinder.

Then insert a blank key into the lock.

Next you'd have to file each tumbler position into the blank.

The idea is when all the positions match, the cylinder turns.

Answer 2

you pour liquid key into the lock, it hardens and you take it out.  Presto!!!!  New key!  Just kidding, I have no freaking idea.