A lock marked “high security” can still be the wrong choice for your door. In a proper lock grades comparison, the first question is not which number is highest. It is which standard applies, what part of the door is being rated and whether the lock works with the rest of your security.
For a homeowner replacing a worn cylinder, a landlord upgrading a rental property or a business responsible for several entrances, the markings on locks can be confusing. British Standards, star ratings, cylinder grades and padlock grades all measure different things. Choosing on the label alone can leave a weak point where you thought you had improved protection.
Why lock grades are not all the same
There is no single grade that covers every type of lock. A euro cylinder, mortice lock, rim lock, padlock and complete door set are tested under different standards because they face different forms of attack.
A euro cylinder is the removable barrel used on many uPVC, composite and aluminium doors. Its rating may relate to resistance against drilling, picking, snapping and other forced-entry methods. A mortice lock is fitted within a timber door and is usually assessed for its resistance to forced entry and suitability for insurance requirements. A padlock grade considers the body, shackle and resistance to physical attack, while a door-set standard assesses the door, frame, hinges, glazing and locking points together.
That is why a “Grade 6” padlock cannot be compared directly with a “3-star” cylinder. Both may be suitable for demanding applications, but they are not measured in the same way.
Lock grades comparison: the standards that matter
For household and commercial doors in Hampshire and Surrey, these are the markings most often worth understanding.
British Standard BS 3621
BS 3621 is one of the most recognised standards for thief-resistant locks on external timber doors. It commonly applies to five-lever mortice sashlocks and deadlocks. Many insurers expect this standard on a final exit door where a mortice lock is used, although individual policies vary.
A BS 3621 lock is normally operated by a key from both sides. This can provide strong security, but it needs sensible key management. In an emergency, occupants must be able to find and use the key to leave the property. Never leave a key where it is visible or reachable through letterboxes, glazing or nearby openings.
For doors where escape without a key is required, such as some shared properties and commercial premises, BS 8621 may be more appropriate. It provides similar security principles while allowing keyless exit from the inside. BS 10621 is designed for situations where a lock may need to be secured from the outside while still offering an internal escape function. The right choice depends on the door’s use, fire-safety arrangements and who occupies the building.
TS007 star ratings for euro cylinders
TS007 is a familiar rating system for cylinders and door furniture. It is especially relevant on doors fitted with euro-profile cylinders, including many modern front, patio and back doors.
A one-star cylinder has a recognised level of attack resistance, but it is generally intended to be paired with a two-star security handle. Together, the cylinder and handle create the three-star level often sought for enhanced protection against snapping and drilling attacks.
A three-star cylinder provides that protection within the cylinder itself. It can be a practical option where a suitable security handle cannot be fitted, or where you want the cylinder to provide the main tested defence. It does not mean the handle, door or fitting quality no longer matters. A poorly fitted cylinder that protrudes beyond the handle can still be vulnerable.
Some cylinders also carry the Sold Secure Diamond standard, often referred to as SS312 Diamond. This is another high-security test for cylinders, with rigorous resistance to common methods of forced attack. It is not simply a higher version of every star rating, but it is a strong indicator that the product has undergone independent testing.
BS EN 1303 cylinder classifications
BS EN 1303 is the European standard used to classify cylinder locks. Its full classification contains several performance categories, covering areas such as durability, corrosion resistance, key-related security and attack resistance. The figures are useful to a locksmith or specifier, but they are less straightforward for a householder reading packaging in a shop.
The practical point is that not every cylinder built to a basic standard offers the same protection against forced attack. If you are replacing a cylinder after a move, a lost key or a break-in concern, ask which anti-snap, anti-drill and anti-pick features are actually included rather than assuming all cylinders are alike.
CEN grades for padlocks
Padlocks are generally graded under BS EN 12320, often shown as CEN grades from 1 to 6. A Grade 1 padlock is for low-risk applications, while Grade 6 is intended for the highest-risk situations and offers greater resistance to attack.
This scale is helpful, but the padlock is only one part of the arrangement. A high-grade padlock on a thin hasp, weak shed staple or lightweight gate chain will not deliver high-grade security. For garages, side gates, storage compounds and business shutters, the fitting point must be at least as strong as the padlock itself.
Choosing the right rating for your door
The right lock depends on the door construction, the location and what is at risk. A front door to a family home needs a different approach from a staff entrance, a communal block door or a garden shed.
On a uPVC or composite front door, a correctly sized three-star cylinder or a one-star cylinder paired with an approved two-star handle may be the sensible starting point. Check that the cylinder sits flush with, or only very slightly beyond, the security furniture. Excess projection gives an attacker something to grip or strike.
On a traditional timber front door, a BS 3621 mortice deadlock or sashlock may be required alongside a nightlatch, depending on the door layout and insurance terms. The frame and strike plate need secure, long fixings into sound timber or masonry. A quality lock cannot compensate for a loose keep or a damaged frame.
For commercial premises, consider how people use the entrance throughout the day. A rear staff door may need a higher-security cylinder, controlled key system, door closer and appropriate escape hardware. A shop shutter may need a purpose-made shutter lock or heavy-duty padlock and hasp. The aim is controlled access without creating an unsafe or impractical route out.
Insurance requirements: check before you buy
Insurers may refer to lock types or British Standards in their policy wording, particularly for external doors. Do not rely on a neighbour’s policy, an old survey report or a general assumption that every insurer requires the same hardware.
Read the policy conditions or ask the insurer to confirm the requirement in writing. If the property has an unusual door, previous damage, a converted garage or a mixed residential and business use, it is worth getting advice before replacing anything. Fitting the wrong lock may create unnecessary cost and still fail to meet the policy requirement.
The grade is only part of the installation
A security rating is earned during a controlled test. Real-world protection also depends on accurate fitting, compatible hardware and the condition of the door. This is where experienced locksmith work makes a material difference.
A cylinder must be the correct length. A mortice lock must be fitted without weakening the door excessively. Keeps, handles and hinges need secure fixings, and multipoint doors need proper adjustment so that hooks, bolts and rollers engage fully. If a door has to be lifted, pushed or slammed to lock, it needs attention before a new cylinder is fitted.
The same principle applies after a burglary attempt. Replacing the obvious broken lock may not be enough if the frame is split, the keeps have pulled away or the door has been forced out of alignment. A full assessment avoids a quick repair that leaves the property vulnerable.
When to upgrade rather than replace like for like
Replacing a failed lock with the same basic type can be appropriate, particularly on an internal door or low-risk cupboard. However, an upgrade is usually worth considering after moving home, losing keys, a tenant change, a break-in attempt or when old hardware shows visible wear.
It is also sensible to review security when adding valuable tools to a garage, storing stock at a business premises or changing the way a building is used. A grade that was adequate for a quiet residential door may not suit a frequently accessed side entrance or an exposed outbuilding.
KBO Lock & Safe can assess the whole opening, explain the relevant standards in plain English and recommend a lock that suits the door, the risk and your budget. The most reassuring choice is not necessarily the product with the biggest number on the box. It is a properly fitted, appropriate lock that gives you dependable protection every time you close the door.
