There is a specific weakness in most UPVC and composite front doors that has nothing to do with the door itself and everything to do with the cylinder inside it. It is exploited thousands of times a year, it takes seconds, and it makes almost no noise.
What cylinder snapping is
A euro cylinder is the barrel-shaped lock that sits in the door, with a keyhole on each side. On many doors it protrudes slightly beyond the door surface, or sits flush, leaving a small portion that can be gripped with a tool.
A standard cylinder will snap at its weakest point under that pressure. The outer portion breaks away, exposing the internal mechanism behind it. That mechanism can then be turned with a simple tool, and the door opens.
The whole process takes seconds and requires no skill or specialist equipment. It is the reason UPVC doors are targeted: the door is secure, but the cylinder is not.
How anti-snap cylinders defeat it
A TS007 3-star cylinder is designed so that, if it is attacked, it snaps in a controlled way at a point that leaves the internal mechanism protected behind a hardened barrier. The exposed part breaks off, but the door stays locked.
What the 3 stars mean
TS007 is the British Standard for cylinder security. One star is awarded for the cylinder's own resistance. Two more stars are awarded to the door's handle and furniture as a set. A 3-star cylinder achieves the full rating on its own, so it works regardless of what handle is fitted.
What insurers require
Most UK home insurance policies now specify a minimum lock standard. For UPVC and composite doors this is normally a TS007 3-star cylinder; for external timber doors it is usually a British Standard BS3621 deadlock.
The requirement is set out in your policy schedule or the security section of your terms. It matters, because a burglary claim can be refused if the property did not meet the standard the policy required at the time.
What it costs
- TS007 3-star anti-snap cylinder, supplied and fitted: £90 – £160
- BS3621 deadlock for a timber door: £95 – £150
- Written specification for your insurer: normally included
Against the cost of a burglary, the loss, the damage, the excess and the effect on your premium, this is one of the cheapest meaningful security improvements available on a modern door.
Checking your own door
Open the door and look at the cylinder from the edge. If it protrudes beyond the door surface, it is a snap target. If it sits flush or recessed, it is less exposed but still worth upgrading unless you know it is already a 3-star unit.
Most cylinders are marked. If yours is not, or you cannot tell, a locksmith can identify it in a couple of minutes and tell you whether an upgrade is worth doing.
5 minute read · updated October 2026
This guidance is written by KMG Locksmiths, an emergency locksmith based in Skelmersdale, West Lancashire, covering a 30-mile radius 24 hours a day.