Bump Keys Threaten Your Personal Security

Bump Keys

I thought long and hard before preparing this post for publication. I had to ask myself a question. “Is this post going to educate the public or educate the criminal.” I looked up statistics on “break and enters” committed with bump keys. I could not find Canadian stats. However, I did find stats from England. In England, approximately 70% of the burglars go through the front door with bump keys. Additionally, more and more burglars in Canada are arrested in possession of bump keys. Therefore, I believe that the crooks already know, and that I need to educate you.

Bump Keys


What are bump keys?

Simply put, bump keys are keys that can open almost any house lock by a simple trick. Some 90% of apartment locks and house locks are vulnerable to a “bump attack”, and it takes only seconds to do. To understand, first examine the workings of a simple lock.

How do keys work?

Look at Illustration 1, on the right. Observe the shear line. When all of the bright yellow pins are aligned perfectly with the “shear line”, the cylinder will turn and the lock will open. As the pins are aligned in Illustration 1, the cylinder will not turn, and the lock will not open.

Bump Keys

Next, look at Illustration 2, on the left. Then observe that the bottom black portions of the pins align perfectly with the “shear line”. Accordingly, the cylinder will turn and the lock will open.

Finally, look at the bumps and valleys in the key, and take notice of how the key actually works. The bumps force certain pins to the height whereat they align with the “shear line”. While the valleys accomplish the same objective by allowing the pins to go deep enough to align.

Therefore, inserting the wrong key, one with the bumps and valleys in different locations, will not create pin alignment, and the lock will not open.

How do bump keys work?

Still looking at illustration 2, notice the yellow portion of each pin. That yellow portion represents the spring. The spring is the part that allow the pins to move up and down and automatically align their tops and bottoms with the “shear line”.

Bump Keys

For a bump key to function properly, it must create the correct pin alignment of both the top and bottom of each pin. But this is less complicated than one might imagine. This is because the top portion will not move in an upward direction past the alignment with the “shear line” unless under extreme pressure. Accordingly, a slight upward pressure is enough to create alignment.

In Illustration 3, look at the left side of the illustration. The pins do not align with the bumps and valleys. Instead, the pin bottoms rest on the upward slopes of the bumps. This is because the key has only been partially inserted into the lock.

Accordingly, if you firm bump (hit) the fob end of the key, you will drive those pin bottoms against the slopes with some amount of force. You can create the proper amount of force with a small tap hammer, or even with the handle end of a screwdriver. Then that jarring force will drive the pins upwards by compressing the springs. In other words, you will force alignment, but only momentarily as the springs will push the pins back down and out of alignment.

Bump KeysIt is all in the timing

Since that alignment is only momentary, you will need to be turning the key at the exact moment that alignment occurs. Therefore, as you “bump” the end of the key, you should already be applying a slight turning motion to it. Accordingly, the unlocking pressure you apply will be “in play” at the brief moment of alignment. This is illustrated in the picture at the start of this blog posting.

There is more

As a burglar, there are a couple of more preparations you will need to make, but as my reader, you don’t need to understand them in order to realize the dangers of bump keys and your vulnerability to them.

There are two types of break-ins from which you need to protect yourself

There is the break-in when you are not home. While disturbing, it does not put you at risk. Far more concerning is the break-in when you are home. Now, there is the added risk of a physical altercation, especially if you area single woman.

How to reasonably protect your front door

I am not a security expert. Therefore, in addition to my recommendation herein, I encourage you to call your local police department and seek its advice on how to secure your residence. That being said, I have two recommendations for you. First, you should purchase an inexpensive lock that will defeat “bumping”. Such a lock will cost under $30, but be certain to ask for a lock that cannot be “bumped”.

Secondly, you should install an additional deadbolt lock on your front door. This lock will not have key access from outside or from inside. It will merely have a turning knob on the inside. One reason for this is that a burglar cannot “bump” or pick a lock that does not have key access. There is also the second very important reason. You do not want to be in a position to have to find a key to exit your residence in the event of an emergency.

Lock bumping is a learned skill. The more often it is practiced the better one will become at it. I can only warn you that those who make a living doing “break and enters” are probably very skilled at it.

Finally, if you reside in an apartment building, you should ask permission to change your lock to one that cannot be “bumped”. If the landlord refuses, a simple application to the Residential Tenancy Branch should easily secure that permission.


Like me on Facebook

Follow me on Twitter @HannonHal

You may post your comments below

About Hal 171 Articles
Ex-golf inventor, Ex-stockbroker, author, blogger, social activist, drug counselor, public speaker


  1. Excellent article, Hal. Very freaky knowing how bump-keys work. Break-ins never used to be this easy. Do those “spool-pins” added to a deadbolt before installation, deter a bump-key type of break-in? A friend of ours paid extra to a Locksmith, to have those spool-pins added to his deadbolts. We don’t know how good they are, yet. Any thoughts?

    • Thank you, Jen. Spool pins make a lock resistant to bumping because of the decreasing diameter of the key path, Short of exotic designs, keyless locks are the only financially viable and effective way to absolutely defeat bump keys, i.e. combination locks, etc.

      • I appreciate that you reply to all our queries and comments!
        We are going to get those spool-pins added to our deadbolts now. Good to know the average homeowner has some protection from break-ins.
        We are hesitant about those combination, keyless locks for homes as what if a thief sees the combo? Thief’s watch their targets and the coming and goings of a residence, don’t they? Also, kids talk…and we wouldn’t want our combo sequence talked about in a school yard in casual conversation.
        A neighbour put on those keyless locks on his house, but regrets it now as he says he is worried constantly about being watched and his wife/kids telling others what the code is. He changes the combo a lot and then tells his wife, but then the kids bug her for it, and on it goes. To me, it’s not worth the hassle…unless a person lives alone.
        We find the best deterrant is having big, working dogs, with loud barks and who watch over our (their) property and street as their job. A burglar would be totally nuts to break into our house, and wouldn’t make it out.
        You are a wonderful writer and blog-host, Hal.

        • I am with you on these combination locks. Not only that they are a pain in a*s in freezing weather as you have to take your gloves off and try to hit the tiny buttons while you shiver. Add to that issue fading eyesight and failing memory and I will stick to key locks, thank you very much.

2 Trackbacks / Pingbacks

  1. How To Make Your Rental More Secure
  2. What Gangford's Near Future Looks Like

Thanks for visiting. Leave a comment!