How to Measure a Euro Cylinder

A euro cylinder is the removable barrel mechanism that sits inside the lock body of a uPVC, composite, or aluminium-framed door. It is secured by a single central screw through the door handle or escutcheon plate, and it operates the multipoint locking system when you turn your key. The cylinder is described by two numbers — for example, 35/45 or 40/50 — which refer to the distance in millimetres from the centre of the fixing hole to each outer edge. The first number is the internal (inside the home) side; the second is the external (outside) side.

Here is the critical point: if the external side of the cylinder protrudes more than a few millimetres beyond the door furniture or escutcheon plate, a burglar can grip it with an ordinary tool and snap it clean off in seconds. This technique, known as cylinder snapping or lock snapping, is well documented and continues to be used by opportunistic burglars across south-east London. A correctly sized cylinder — ideally one rated to TS007 3-star or at minimum combining a 1-star cylinder with a 2-star door handle — eliminates this vulnerability almost entirely. Getting the measurement right is therefore not merely a matter of a good fit; it is a genuine security issue.

You will need a flat-bladed screwdriver and a tape measure or steel rule. Start by opening your door so you have easy access to both sides. Remove the single screw on the edge of the door that holds the cylinder in place — it passes through the door edge, through the lock body, and into the cylinder itself. Once the screw is out, insert your key into the external keyhole, turn it about 20 to 30 degrees to retract the cam (the small metal tongue at the centre), and pull the cylinder out toward you. You now have the cylinder in your hand and can measure it accurately. Measure from the centre of the fixing hole to the external end of the cylinder, then from the centre of the fixing hole to the internal end. Write both measurements down: internal measurement first, external second, separated by a forward slash — for example, 40/50. The total length is 90 mm in that example. If you are buying a replacement, match these figures exactly.

One point that catches many homeowners out: if you cannot remove the cylinder because the door is already locked in a compromised position, measure on the door while the cylinder is still in place. Place your tape measure at the centre of the fixing screw hole on the door edge, then measure outward to the face of the door on the internal side — note that number, then measure to the face of the door on the external side, and add approximately 10 mm for the escutcheon plate thickness. That gives you a working estimate, though removing the cylinder and measuring it directly is always more accurate. When in doubt, call our team at 020 3757 5689 and we can confirm the right size on-site before we fit anything.

When a cylinder extends beyond the external door furniture — even by 5 or 6 millimetres — it creates a purchase point. A burglar can apply rotational force with a simple hand tool and, in a matter of seconds, shear the cylinder at its weakest point, which is typically just behind the external cam. Once the front section has snapped away, the remaining internal section can be manipulated directly to operate the multipoint locking system without a key. The whole process is fast, almost silent compared to other forced-entry methods, and leaves little visible damage to the door frame.

This is why choosing the correct size matters as much as choosing a quality cylinder. Even the most robust anti-snap cylinder on the market becomes a liability if it protrudes excessively. The correct approach is to fit a cylinder that sits flush with or very slightly recessed within the escutcheon plate on the external face — typically no more than 1 to 3 mm proud — so there is no grip point. If you live in a property where door lock replacement Bexleyheath is overdue, particularly on an older uPVC door where the cylinder is the original factory-fitted unit, it is well worth having the whole assembly checked. We carry anti-snap, anti-drill, anti-pick cylinders that meet TS007 standards and can advise on the right specification for your door during a visit.

These four terms are often used interchangeably, but they mean different things and lead to different jobs. Replacement means removing an existing cylinder or lock mechanism and fitting a new one of the same type in the same position — the most common job we carry out, particularly on uPVC doors where the cylinder has worn, been damaged, or failed a security audit. Installation refers to fitting a lock mechanism on a door that has not previously had one, or converting a door to a different lock type entirely — for example, upgrading a back door from a simple nightlatch to a full mortice deadlock or a multipoint system. A lock change Bexleyheath typically falls under replacement, though the term is sometimes used loosely to describe switching from one lock type to another.

Repair is the right word when the existing mechanism is repairable — a loose handle, a stiff cylinder that has not yet failed, a misaligned multipoint lock that is not engaging properly, or a uPVC door lock repair Bexleyheath situation where the gearbox has partially seized but the door is still functioning. A change, in everyday language, usually means swapping out the cylinder without touching the lock body — the quickest and most cost-effective option when the rest of the door hardware is sound. If you are unsure which category your situation falls into, the safest approach is to describe what the door is doing (or not doing) and let us assess it on arrival. We confirm the exact scope and quote before any work begins, so there are no surprises on the invoice.

Not every euro cylinder problem announces itself dramatically. Sometimes the warning signs are subtle: a key that requires more force than it used to, a cylinder that feels gritty or stiff in cold weather, a door that has started catching on the frame and preventing the multipoint hooks from engaging fully. Left unattended, these issues tend to worsen — and they often reach a crisis point at the most inconvenient moment, such as late on a Sunday evening or on a bank holiday, which is exactly when we receive the most calls from residents who are locked out Bexleyheath after a cylinder has finally given up. Our team is available around the clock as an emergency locksmith Bexleyheath and we send a locksmith straight away when you call — we are usually with you in about 30 minutes, though we never promise an exact time since road conditions and call volume vary.

If you are already locked out when you are reading this, the first thing to do is check every other potential entry point calmly and systematically: a back door, a ground-floor window that may be on the latch, a neighbour or family member who holds a spare key, or a letting agent if you are a tenant. If none of those options apply, do not attempt to force anything — forced entry risks damaging the door frame and the lock body in ways that make a subsequent proper repair more complicated and more expensive. Call 020 3757 5689 and our 24 hour locksmith Bexleyheath team will handle it correctly from the outset. The price we quote on the phone is the price you pay — we confirm everything up front before we travel to you, and the final figure will depend on factors including the lock type, any parts needed, the time of call, and your location within our coverage area.

While this guide has focused on euro cylinders, it is worth briefly noting the full picture of door lock work we carry out locally. Many Bexleyheath properties — particularly the older terraced houses on streets like Watling Street and around the DA6 and DA7 postcode districts — have a Yale-type nightlatch (a rim lock cylinder on the front door) alongside a 5-lever mortice deadlock lower down. Insurance policies in the UK frequently require the mortice deadlock to meet BS3621, and we can verify and upgrade both locks during the same visit if needed. For night latch and rim cylinder replacements we follow the same size-verification process as for euro cylinders, ensuring the new rim cylinder is the correct diameter and throw for the existing nightlatch body.

For mortice lock replacements — covering both deadlocks and sash locks — the key measurements are the backset (from the face of the door to the centre of the keyhole), the case size, and the follower size. These determine compatibility with the existing mortice pocket cut into the door. Swapping a mortice lock without checking these figures can result in a lock that physically cannot be operated, so accurate measurement before purchase is just as important as it is with euro cylinders. Whether you need a straightforward euro cylinder swap, a full door lock replacement Bexleyheath, a nightlatch upgrade, or a mortice deadlock that meets current insurer requirements, our experienced team carries the most common sizes and grades as standard on the van, so most jobs are completed in a single visit. For anything outside the ordinary, we source parts quickly and return at a time that suits you.

Our team handles the full range of residential door lock work across Bexleyheath and the surrounding DA postcode districts. The services we carry out day-to-day include: euro cylinder replacements (all sizes, including anti-snap TS007-rated); euro cylinder upgrades to 3-star or combined-rating specifications; nightlatch and rim lock cylinder replacements; nightlatch body replacements; 5-lever mortice deadlock replacements (BS3621 where required); sash lock replacements; multipoint lock gearbox replacements; multipoint lock mechanism upgrades; uPVC door lock repair including hook and roller replacements; composite door lock servicing and replacement; aluminium door cylinder and lock body work; front door lock changes following a lost or stolen key; lock changes after a tenancy change or property purchase; emergency lock replacement following a break-in or attempted forced entry; anti-snap cylinder fitting on existing multipoint doors; door handle and escutcheon plate replacement where the furniture has been damaged; door barrel re-alignment where misalignment is preventing the cylinder from turning; door frame repair and reinforcement following forced entry; patio door lock cylinder replacement; French door lock replacement on both active and passive leaves; communal entrance door cylinder replacement (with managing agent authorisation); landlord lock change between tenancies; lock-out service with non-destructive entry where possible; damaged cylinder removal where the cylinder has been snapped or drilled; and full door security assessments covering cylinder grade, door furniture, letterbox protection, and frame integrity.

Once you have your measurements, you face a choice of cylinder quality. At the basic end are standard euro cylinders with no additional security features — these are adequate only for low-risk internal doors and should not be used on any external door in a residential property. Mid-range cylinders offer anti-snap protection through a sacrificial section that breaks away before the operational part of the cylinder is compromised. At the top end, cylinders rated TS007 3-star combine anti-snap, anti-drill, anti-pick, and anti-bump protection and are tested to a British Standard. Some insurers now explicitly request TS007-rated hardware as a condition of cover, particularly for doors in areas with recorded burglary activity.

One practical note: when you buy a replacement cylinder, it will come with new keys. If your front door currently operates on a master key or a key-alike system — for example if the same key opens a communal entrance and your flat's own front door — a standard off-the-shelf cylinder will break that arrangement. In that situation it is worth discussing your requirements before purchase rather than after. Our team can advise on the right cylinder specification for your specific door and situation during the call or on arrival, and we carry a range of grades as standard so there is no need to source parts separately before we attend.

Being locked out Bexleyheath is stressful, particularly if it happens in the evening or at a weekend. Before calling us, run through a short checklist: is there a back door or side gate access that may be unlocked; does a family member, friend, or neighbour hold a spare key; if you are a tenant, does your letting agent have a key-holder contact for out-of-hours situations; and is there any ground-floor window that is on the latch and can be opened safely from outside without causing damage. If any of those options exist, pursue them first — it may resolve the situation without any call-out needed.

If none of those apply, call 020 3757 5689 and we will send a locksmith straight away. As an emergency locksmith Bexleyheath, we are on the road around the clock, covering the town centre, the streets around Bexleyheath station, Barnehurst, Northumberland Heath, Welling, and throughout the DA6 and DA7 areas. We will confirm the price before we travel and aim to arrive in about 30 minutes, though we do not guarantee a specific time. When we arrive, we will always attempt non-destructive entry first to preserve your existing lock and keep any additional work to a minimum.