What Is Lock Bumping and Is Your Lock at Risk?
Lock bumping is a way of opening many standard pin tumbler locks without the right key and often without obvious damage. Here's how it works, which locks are at risk, and what to do about it.
Short answer: lock bumping uses a specially cut key, tapped while being turned, to jolt the pins inside a standard pin tumbler lock so the lock opens. Many common, lower-cost cylinders can be vulnerable. The fix is to fit cylinders designed to resist bumping, add a deadlock or a restricted key system, and secure the other ways into the house.
How lock bumping works
Most house locks are pin tumbler locks. Inside are pairs of small pins sitting across the line where the cylinder turns. The right key pushes each pair to exactly the right height, so the gap between them lines up and the cylinder can turn.
A bump key is cut so that, when it's tapped, it transfers a sharp jolt to the pins. For a split second the top pins jump above the shear line, and if the key is being turned at that moment, the lock opens. It's the same principle as a cue ball hitting another ball.
Which locks are at risk
- Standard pin tumbler cylinders, especially older and lower-cost ones
- Locks with worn pins or loose tolerances
Locks that are harder to bump include:
- Anti-bump or high-security cylinders with special pins or designs
- Restricted key systems, which use controlled key profiles
- Locks that don't use a standard pin tumbler, such as some electronic and smart locks (which have their own considerations)
Signs a lock may have been bumped
Bumping often leaves little trace, but you might notice:
- small fresh marks or dents around the keyhole
- a lock that suddenly feels different, stiff or rough
- signs of entry with no forced door or broken window
If you think someone has got in, contact Victoria Police (000 if it's happening now, or 131 444 for the Police Assistance Line), and get the locks rekeyed or replaced.
How to protect your home
- Fit anti-bump or high-security cylinders on external doors.
- Add a deadlock to back and side doors that only have a latch. See deadlatch vs deadlock.
- Consider a restricted key system, which also stops unauthorised copies of your keys.
- Don't forget the easier ways in. Sliding doors and windows are often easier than any lock. See how to secure a sliding door and window locks.
- Replace worn locks, which are easier to manipulate.
Should you worry?
Lock bumping is rarely the easiest way into a house. Doors left unlocked, open windows and weak sliding doors are usually simpler targets. Upgrading cylinders is worth doing, but it works best as part of securing the whole house.
On the Mornington Peninsula or in Frankston? See lock changes and rekeying and security upgrades.
Frequently asked questions
Your questions, answered
What is lock bumping?
A way of opening a pin tumbler lock with a specially cut "bump key" that is tapped while being turned, jolting the pins so the lock opens.
Are all locks vulnerable to bumping?
No. Many standard pin tumbler locks can be, but anti-bump and high-security cylinders are designed to resist it.
How can I tell if my lock has been bumped?
There are often few signs. Look for fresh marks around the keyhole or a lock that suddenly feels different.
How do I stop lock bumping?
Fit anti-bump or high-security cylinders, add deadlocks, and consider a restricted key system.
Is lock bumping common?
It's rarely the easiest way in. Unlocked doors, open windows and weak sliding doors are usually simpler targets, so secure those as well as upgrading locks.
Need a locksmith on the Peninsula?
Homes, cars and businesses. Call any time and tell us what has happened.