Of all the ways to pick a lock Impressioning is one of the most exquisite techniques available. Because, not only do you open the lock without the correct key, you also end up with a working key, meaning you will never have to pick it again. That's right, amazing isn't it!
Impressioning is where you insert a blank key into the lock and manipulate it in such a way the lock leaves tiny impressions on the blank. These impressions are then filed down, and the process is repeated. After several cycles of taking and filing impressions, the key suddenly turns in the lock and it's open, and you know you've succeeded. But you also have a working key - awesome!
Experts such as world champion lock pickers Oli Diederichsen (who wrote the book we stock) and Jos Weyers (who demonstrated impressioning with out tools at a UK BUMP KEYS workshop a few years ago) can impression locks in under a minute. SO with a blank key and a few tools, they have the lock opened and a working key in 60 seconds. Wow!
Glardon Vallorbe Swiss #4 140mm Impressioning File
Lock Pickers Vice Mk2