The art of key impressioning has been around for hundreds of years, with only a handful of locksmiths using this traditional technique.
What is key impressioning?

Starting with the right profile key blank which is then filed down to open the lock.
This technique can take quite a long time to perfect, but once mastered, there’s nothing more satisfying than being called out to a locked door, and with a little patience and time you have a fully working key to your door.
This prevents the lock from being drilled open (Destructive entry)
Some of the latest modern anti-snap locks would prove much harder to do with this method so the locksmith would probably use the latest tool to pick open the lock were possible.
The Technique Process

Start with the right key blank that fits the lock perfectly.
While the key is inserted, using moderate force on the key, rock the key up and down, turning the key in either direction at the same time.

Using too much force will BREAK the key, Using too little wont mark the bottom of the key blade.
Using a magnifying aid will assist you to see the marks left after the rocking process.
On the marks were visible, remove some material by filing, bit by bit not too much at first.
Repeat this process again and again and again.
If this is done correctly all of a sudden the key will turn your lock (MAGIC)
You now have created a fully working key.