what is Key Impressioning

Key Impressioning: A Skill Every Lock Enthusiast Should Know

The process of producing markings on a blank key with the binding pins and then shaping it until a working key for the lock is produced is called key impressioning.

The goal is to use the blank key to identify the blocking pins thus allowing the locksmith to identify the portion of the key that needs to be filed down.

Small marks or impressions are left by the lock on the blank key thus giving us the name for this technique. There are other methods of impressioning a key that we will cover in future articles.

Key impressioning can be the next step or skill developed in one’s locksport career.

Key Impressioning Basics

This method is another method of “attacking” a lock. It could be done in the field but would definitely take additional skills and good lighting. Reading the impressions is one of the important steps to key impressioning.

As with other covert entrance methods, please follow all laws and guidelines.

Key impressioning is a non-destructive method of creating a working key without disassembling the lock. As such, it is a plausible method to gain entry or open a lock even if you may have lost or misplaced the original key(s).

Gathering a few simple tools together will allow you to get started.

Key Impressioning Tools

A key impressioning kit is a collection of tools and supplies needed for a key impressioning kit.

This kit can be as cheap and budget-friendly or extravagant as you want.

The basic essentials are:

  • A lock
  • A blank key
  • A file

That’s it! We have a few additional recommendations that we believe are worth the small cost.

The Lock

For the lock in this learning session, we recommend a pin tumbler lock such as this Master Lock No. 5 (Paid Link) or this Abus 55/40 (Paid Link). They can be found on Amazon or your local hardware store for fairly cheap.

These locks can be low-security lock additions to your collection for developing your early locksport skills. Check out this article on how to go about picking your first lock here.

The Key Blank

Key blanks and cut key for impressioning

Next up, we will need some key blanks for these specific locks. We strongly recommend purchasing at least 3 key blanks.

Even though you won’t have any issues if you follow our advice, key blanks break so we recommend having a few backups just in case.

It is important to know a few details about your lock.

If possible, try to identify the make and model. If using our example locks, you are all set.

The next important thing to know about your lock is the number of pins. The make and model of the lock will reveal that with a quick internet search.

The number of pins will narrow down the key type we need that is suitable for our lock.

Don’t worry, in this guide, we have linked our recommended key blanks.

The Abus 55/40 key blanks are available on mrlock.com and the Master Lock No. 5 key blank can be found on easykeys.com.

*A good hardware will likely be able to sell you the correct key blanks as well. I recommend bringing the lock-in with you for this method.

The File

In our research and own key impressioning trials, we have discovered a rounded Swiss Number 4 file (Paid Link) works well.

If you are on a budget, this cheap file set (Paid Link) will do the job. I have been using it to shape my own lock picks as well.

Tool Upgrades

For an upgraded toolset for your key impressioning tool kit, we have some additional recommendations.

First, purchase some sheets of sandpaper (Paid Link) in these roughnesses: 400, 600, and 1000 grit

Due to the need to identify the smallest of markings on the key blank, we recommend a magnifying glass (Paid Link) or jeweler’s loupe.

Next, our next recommendation is highly recommended for key impressioning as well as in general lock sport.

We recommend purchasing a vice (Paid Link) for holding your locks while key impressioning as well as for during a lockpicking session.

Finally, having locking pliers (Paid Link) during this process as well. It allows you to apply torque on the key during the impressioning step.

Now, we are fully equipped and ready to begin.

Key Impressioning Process

Prepping the Key Blank

First, let’s sand the top edge of the key blank.

This will remove any machine markings, polish or paint.

It gives us the blank canvas we need.

Pin Locator

Next, insert the newly prepped key blank fully into the lock.

You may use the locking pliers to hold the key firmly.

With the key blank inserted entirely, apply light rotational torque going back and forth with the key.

Remove the key. Are there markings clearly visible along the top of the key? If not, repeat and apply additional pressure as you turn the key.

Once you have clear marks on the key, we highly recommend drawing straight vertical lines along both sides of the key. This will help us identify and remember where the lock pins are located.

Initial Filing

Now with the pin locations identified along the key blank ridge, we can make our first markings.

Our key blanks are 0 cuts with most keys beginning at a deeper cut for their biting.

Take the file firmly and glide it in one direction along the top of the key blank where we have the pin locations.

These filings should be perpendicular to the key and grow in one direction.

Repeat this process until there are small grove indications of the pin locations.

These groves should be just deep enough to show the pin locations and fall along the vertical line markings we made earlier.

Impression Me Like One of Your French Locks

With the foundation of the process in place. We repeat the key impressioning process until we have a consistently working key. It goes as follows:

  1. Insert the key into the lock.
  1. Jiggle the key in the lock.
    • Turn the key
    • Trying pushing it up into the pins
  1. Remove the key from the lock
  1. Under the magnifying glass or loupe, inspect the key for markings
  1. File the key down with quick one-direction strokes of the file, perpendicular to the key
    • TIP: Do not file markings you don’t see!
    • If you don’t see any markings, but the key still doesn’t open, try “impressioning” the key more aggressively going forward
  1. Clean the metal shavings off the top of the key blank
    • This ensures a clean working surface for the next round of “impressioning”
  1. Repeat the process

Continue impressioning, filing, and cleaning until the key opens the lock.

Open sesame

Soon your lock will open! Congratulations!

If possible, compare your key to the original working key.


Note how much pressure you use when trying to rotate the key to mark it.

You can attempt to single-pin pick the lock to get a better understanding of the pinning heights.

Be patient. Observe the markings closely.

Using the 1000-grit sandpaper may help identify new markings between impressioning efforts.

Other impressioning methods

There are other methods of key impressioning involving clay, foil, or silicone. These methods are also non-destructive.

We will explore these different methods in future articles.

The method we described in this article is called hard key impressioning.


The ability to understand and perform the process of key impressioning can open a whole new arena of locks, keys, and locksport. It takes a certain amount of skill and patience, much like lock picking.

We hope this explanation and guide have been helpful in your introduction to key impressioning.

If you enjoyed this article, please check out our other articles here at Lock Judge.

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