Most front doors in flats and chalets lock with a euro cylinder: the part you put the key into. It is also the part most break-ins go for, because it is the weakest point of an otherwise solid door. There are three common ways in through it, plus one that ignores it altogether.
Snapping
How: the cylinder is gripped where it sticks out of the door and twisted until it breaks at its thinnest point, the middle. With the outer half gone, the lock can be turned by hand.
What gives it away on your door: a cylinder that stands proud of the handle or plate by more than a few millimetres.
What stops it: a cylinder with snap protection, built to break at a sacrificial line outside the lock and leave the working part intact; and a guard plate that covers the cylinder so there is nothing to grip.
Bumping
How: a doctored “bump key” is put in and tapped, so that the pins inside jump for a split second and the cylinder can be turned. It leaves little or no mark.
What gives it away: nothing you can see. Ordinary cylinders are vulnerable; older ones almost always.
What stops it: a cylinder certified anti-bump, with pins that cannot be bounced into place.
Picking
How: the pins are set one by one with fine tools. It takes skill and time, which is why it is less common in burglaries than people think.
What stops it: better cylinders with security pins, which make picking slow enough not to be worth it.
Drilling and prying
How: drilling through the cylinder, or levering the door away from the frame until the bolt comes out of the keep.
What stops it: hardened inserts in the cylinder against drilling, and a strong keep fixed with long screws into the wall, not just the frame, against prying. A multipoint lock, which bolts the door in several places, makes prying much harder.
So what should you check?
- Does the cylinder stick out? If yes, snapping is the first risk.
- Is there a guard plate? If not, one is worth fitting.
- How old is the cylinder? If you do not know, assume it offers no bump protection.
- Does the door bolt in more than one place?
The answers decide whether a straight lock change is enough or the door wants an upgrade. If you have already found marks on your lock, read what to do when the lock feels wrong, and for business premises, what to check at a Riodel unit.