Bumping, picking and cylinders: what actually protects you

The armoured door that protects nothing

This is the most widespread misunderstanding in the trade. An armoured or reinforced door resists brute force: the crowbar, the kick, the screwdriver in the frame. Against that it works very well.

But the vast majority of break-ins are not brute force: they go through the cylinder, the small part you put the key into. And if your armoured door has a basic cylinder, you have a safe with a suitcase lock on it. The door is fine; what needs changing costs a fraction of what the door did.

What bumping actually is

A key filed down to maximum depth on every tooth is inserted into the cylinder and struck sharply while turning pressure is applied. The impact sends an impulse through the pins, which jump for a fraction of a second, and in that instant the cylinder turns.

What matters to you: it is fast, it is quiet, it leaves no visible mark and it takes very little skill. The no-mark part is the real problem, because your insurer may want signs of force to cover a theft and there will not be any.

An anti-bump cylinder stops it. It uses irregularly shaped pins, counter-pressure elements or magnetic components that do not respond to that impulse. It is not magic and it is not expensive.

Picking, snapping and drilling

Classic picking — moving the pins one by one — takes real skill and time, which is why it is less common than films suggest. A cylinder with anti-pick pins stretches it until it stops being worth anyone’s while.

Snapping is cruder and far more common: the cylinder is gripped at the face and pulled out. Against that, a cylinder with a designed break point works — it snaps where it is meant to and leaves the mechanism locked — and above all a protective escutcheon, that steel plate around the cylinder. A good escutcheon is one of the best value-for-money things on a door.

Drilling is the last resort and the noisiest. Decent cylinders carry hardened steel inserts that destroy the bit.

What to look at on your own door this afternoon

Open the door and look at the edge of the cylinder, where the brand is stamped. If there is no brand, or one you cannot find anywhere, it is almost certainly the one the developer fitted: the cheapest on the market that month.

Look at whether the cylinder sticks out past the escutcheon. If it protrudes more than two or three millimetres, that is a handle for pulling it out. It should sit almost flush.

And check the calendar in your head: if it has not been touched in fifteen years, or it is the original from when the building went up, it is protecting very little.

What is worth it and what is not

Very much worth it: swapping a basic cylinder for an anti-bump, anti-pick one from a known brand, with an escutcheon. It is a fraction of the price of a door and it defends the way people actually get in.

Sometimes worth it: a key with card-protected copying, if you are worried about who holds copies — a rented flat that has been through several hands, a building with a lot of loose keys.

Usually not worth it: replacing a whole door for security when the one you have is sound and only carries a bad cylinder. That is spending ten times more to close the same gap.

Common questions

How do I know if my cylinder is anti-bump?

Send a photo of the edge, where the brand is stamped. The make and model tell us what protections it has, and you will be told even when the answer is that you are already fine and nothing needs changing.

Is a card-protected key worth it?

If you are worried about how many copies are out there, very much: without the card nobody can cut a copy, not even you. If you live somewhere the keys are accounted for, that money does less for you than a good escutcheon.

Is changing the cylinder a building job?

No. It is half an hour, the door and the frame are not touched, and it is nearly always done on the spot. Only the turning part is replaced, not the whole lock.

What we do about this

• High-security locks
• Euro cylinder change