When you lose a key and call a locksmith, most of the time one of two things will happen... they will either pick the lock or drill it. In either case you're typically left with a door that's open, but not with the means of operating it again.
What if we told you that you could not only open a lock but also /create a working key/ out of nothing at all in ways that are nearly undetectable. With a blank key, a file, a keen eye, and a bit of time, it is easily done... through the art of impressioning.
Learn how this skill is used and you'll see that not only can you often gain access ONCE, but again and again and again.