Impressioning 101

Impressioning is covert, non-damaging technique used to create a working key from a lock.

When torque is applied to a cylinder, pins bind with varying degrees of pressure corresponding with their height. By inserting a blank key into a lock any applying torque and movement, the pins leave subtle marks or 'impressions' on the blank. These marks are carefully identified, and the blank is filed where marks are present. By repeating this operation, a working key is produced.

Impressioning has three main advantages over picking:

1. Pick many times, impression once
   When a lock is successfully impressioned, you have a working key, which can be re-used and even copied.
   
   When picking, a lock must be re-picked every time you want to open it (and often every time the plug is turned)
2. Progress is not lost
   If interrupted while picking, progress is lost, and the process must be restarted.
   
   When impressioning, progress is 'saved' onto the key. Depending on access to the lock, an impressioning session can be spread out over hours or even days.
3. Bypass High-Security
   While anti-picking techniques are common, anti-impressioning techniques are far less common. A high-security lock with anti-pick pins may be difficult to pick, but easy to impression.
   
   Impressioning also works on dimple and warded locks.

If you're looking to get started with impressioning, Lock401 has a curated kit of tools dedicated to impressioning: The Lock401 Impressioning Kit.

If you're interested to see impressioning in action, the following video is a great starting point: