What Are British Standard Locks?

7th June 2026 by Tom Lamb · Updated 18th August 2026

“British Standard lock” usually means a lock assembly that has been tested against a specific British Standard and can demonstrate conformity through appropriate marking/certification. For many traditional timber entrance doors, BS 3621 is the familiar thief-resistant lock standard where a removable key is required for egress. BS 8621 covers thief-resistant single-point lock assemblies that can be unlocked from the inside without a key. Modern uPVC and composite doors often use a different standards route: their euro cylinders may be rated to TS 007, while PAS 24 relates to the security performance of a complete doorset rather than one replacement lock.

That distinction matters. “Five lever”, “anti-snap”, “insurance approved” and “British Standard” are not interchangeable phrases. The standard must suit the hardware and door, and your insurer can set its own minimum-security conditions.

If the markings on your lock are unclear, APEX Locksmith & Joinery can assess the actual door and hardware rather than relying on a label or key shape.

Originally published: 7th June 2026  |  Last updated: 18th August 2026

What Does “British Standard” Mean?

British Standards are published by BSI and set out defined requirements and test methods. In the lock context, a standard may address thief resistance, operation, egress and the components included in the lock assembly. A product claiming compliance should be assessed against the correct edition and scope rather than simply carrying generic “high security” marketing.

BSI currently lists BS 3621:2017+A1:2024 as the standard for lock assemblies operated by key from both inside and outside. The scope is for thief-resistant mechanically operated single-point lock assemblies and specifically separates this from the keyless-egress arrangements covered by BS 8621.

BS 3621 Explained

BS 3621 is one of the best-known residential security standards in the UK. It applies to qualifying single-point lock assemblies that are key-operated from both sides, meaning a removable key is needed to unlock from the inside. This makes it appropriate only where that egress arrangement suits the door and occupancy.

It is commonly seen on mortice deadlocks, sash locks and some rim arrangements for timber doors. Do not assume every lock with five levers meets BS 3621. Lever count is a design characteristic; compliance with BS 3621 means the complete qualifying lock assembly has met the relevant performance requirements.

BS 8621 Explained: Keyless Escape From Inside

BS 8621 covers thief-resistant single-point lock assemblies that can be unlocked from the inside without a key, such as by a handle or thumbturn, while still being key-operated from outside. This is an important distinction where occupants must be able to escape without searching for a removable key.

BSI lists BS 8621:2017 as current and under review. Choosing between BS 3621 and BS 8621 is therefore not about which number is “higher”; it is about the required security and egress behaviour of the door.

What About BS 10621?

BS 10621 covers thief-resistant lock assemblies with a dual operating concept: a normal keyless-egress mode and a secure mode in which egress can be prevented. BSI lists BS 10621:2017+A1:2024 as current. This is more specialised than the everyday question of choosing a front-door mortice lock, but it shows why the BS 3621/8621/10621 family must be understood by function rather than by assuming one standard replaces another.

TS 007: Why It Is Different From a British Standard Number

TS 007 is a technical specification developed for enhanced security of replacement cylinders and associated hardware. It became particularly important because euro cylinders can be attacked independently of the rest of the multipoint lock. DHF's current publications list TS 007-1:2024 + A1:2026 for replacement cylinders/security hardware.

A familiar domestic solution is a TS 007 Kitemarked 3-star cylinder, or a compliant combination that achieves the required total star protection using cylinder and protective hardware. Sold Secure Diamond SS312 cylinders are another recognised route referenced by security guidance.

BS 3621 vs TS 007: They Are Not Competing Versions of the Same Lock

What Is a BSI Kitemark?

The BSI Kitemark is a third-party certification mark used across many product categories. On locks and cylinders, the useful information is the Kitemark together with the specific standard/rating shown. A Kitemark by itself does not tell you whether the product is a BS 3621 lock assembly or a TS 007 cylinder.

Look at the faceplate, cylinder face, security furniture and documentation. Markings should be legible enough to identify what is actually certified.

How to Check a Timber-Door Lock

How to Check a uPVC or Composite Door

On these doors, the lock usually consists of a multipoint mechanism controlled by a euro cylinder. The relevant homeowner check is therefore often the cylinder rating and protective furniture rather than looking for BS 3621 on the multipoint strip.

If the cylinder is the part being upgraded, APEX's uPVC window and door repair service can also assess whether stiffness or poor locking is actually caused by door alignment or gearbox wear.

Why “Five Lever” Does Not Automatically Mean BS 3621

“Five lever” describes part of the internal lock design. BS 3621 is a performance standard for the lock assembly. A lower-cost lock can have five levers without satisfying the full standard. If your insurer specifies BS 3621, look for the actual certification/marking rather than relying on the words “five lever” in an online listing.

What Does “Insurance Approved” Really Mean?

There is no single universal product list that makes a lock “approved by every insurer”. Insurers write their own policy conditions. One may ask for a five-lever mortice deadlock conforming to a specified standard; another may accept an equivalent arrangement or have different wording for uPVC/multipoint doors.

BS EN 1303: What Does It Tell You About a Cylinder?

BS EN 1303 is a classification standard for cylinders, covering characteristics such as durability, key-related security and attack resistance. It is useful technical information, but homeowners should not assume that any cylinder carrying an EN 1303 classification automatically provides the same anti-snap performance as a current TS 007 3-star or Sold Secure Diamond cylinder.

When lock snapping is the concern, look for the relevant enhanced-security certification rather than one generic standards number.

PAS 24: Think About the Complete Door

PAS 24 is commonly used for enhanced security performance of doorsets/windows. A doorset is the complete assembly: door leaf, frame, glazing where present, hardware and locking arrangement. This is important when buying a new door because tested security is stronger evidence than assembling unrelated high-security components and assuming the combination performs as a system.

A replacement cylinder can improve an older door, but it cannot turn every weak doorset into a PAS 24 doorset.

What Standard Should You Look For by Door Type?

Standards Change: Check the Edition, Not Just the Number

Standards are revised to reflect new attack methods, products and test practice. As of August 2026, BSI lists BS 3621:2017+A1:2024 as current, while DHF lists TS 007-1:2024 + A1:2026 for replacement cylinders/security hardware. This is why an old web article quoting a decade-old revision can be technically behind even when the broad advice remains recognisable.

When Is a Lock Upgrade Worthwhile?

• The existing lock/cylinder has no identifiable modern security certification.
• A euro cylinder projects excessively from the outside furniture.
• You have moved home and key control is unknown.
• Keys have been stolen or lost with address information.
• The lock has been attacked or damaged.
• Your insurer has a specific security condition that the current hardware does not meet.
• The existing lock is unreliable, worn or difficult to operate after door-alignment issues have been ruled out.

When a Higher Standard Does Not Fix the Real Problem

Security hardware only works as part of the door. A premium lock in rotten timber, loose handles around a high-security cylinder, weak glazing next to an internal thumbturn, or a multipoint system that barely engages the keeps are examples where the badge on the lock is not the whole answer.

How a Locksmith Should Approach a Standards Upgrade

The sensible sequence is to identify the door, confirm current hardware/markings, understand the security and egress requirements, check the frame/operation, and then specify compatible parts. APEX's wider locksmith services include lock upgrades and repairs, so an upgrade can be based on the whole door rather than a single product label.

Certification, Compliance and Marketing Are Different Things

A manufacturer can describe a product as “high security” without that phrase defining a test. A product may be designed to a standard, tested by a laboratory, or third-party certified under a scheme such as the BSI Kitemark. For homeowners, third-party certification and clear product marking provide stronger evidence than a vague security claim on packaging.

Read the Marking Beside the Kitemark

Mortice Deadlock vs Sash Lock vs Rim Lock

BS 3621 describes a performance standard, not one physical shape. A mortice deadlock contains a key-operated bolt; a mortice sash lock combines latch and deadbolt; certain rim lock assemblies can also fall within thief-resistant standards. The product has to be certified in its actual configuration. Do not assume “mortice” itself means secure or that a night latch automatically meets the same standard.

Single-Point Standards vs Multi-Point Standards

BS 3621/8621/10621 in their commonly discussed form address single-point thief-resistant lock assemblies. Multi-point doors have separate standards/specifications and complete-doorset test routes. This is another reason a uPVC door should not be assessed by searching its long locking strip for a BS3621 stamp.

How TS007 Star Combinations Work

The aim is to protect the cylinder against a defined enhanced attack level. A 3-star cylinder can provide the required cylinder-level solution on its own, while a 1-star cylinder can be used with qualifying 2-star protective hardware in a compliant combination. For a homeowner who wants a straightforward replacement, a clearly certified 3-star cylinder is often easier to identify and maintain.

Always check the current product certification rather than adding star symbols from unrelated components that were not intended to work as the required combination.

Why Cylinder Projection Matters Even With a Good Rating

A correctly specified euro cylinder should fit the door and protective furniture. Excessive external projection gives more physical exposure and can indicate the wrong length. Security testing does not give permission to install the component badly. Measure from the central fixing screw to each end and match internal/external dimensions to the actual door.

Standards and Flat Entrance Fire Doors

A flat entrance door can have both security and fire/smoke responsibilities. Do not change a lock, thumbturn, closer or other ironmongery solely to chase a security standard without checking compatibility with the fire-resisting doorset and the need for safe egress. In many flats, the ability to escape without finding a removable key is a critical design consideration.

What If an Old Lock Shows an Earlier BS Edition?

A previous edition on an existing serviceable lock does not automatically mean the lock suddenly became illegal when the standard was amended. Whether an upgrade is needed depends on the policy requirement, security risk, condition and building context. For new purchases, use current products/certification; for existing hardware, assess rather than replacing solely because a newer amendment exists.

What If There Is No Visible Marking?

Lack of a visible mark can mean the lock is uncertified, the marking is hidden/worn, or documentation has been lost. If insurance or a specification depends on proving the standard, uncertainty is a problem in itself. A locksmith may identify the product from the faceplate and construction, but when evidence cannot be established, replacement with clearly documented current hardware can be the simplest route.

British Standards After a Burglary Attempt

Do not focus only on whether the lock “passed” the attack. Inspect the entire door: cylinder, handles, lock case, keeps, hinges, frame, glazing and fixings. A certified lock can remain functional while surrounding material has been weakened. Security restoration should return the whole opening to a reliable condition.

Smart Locks and Standards

Electronic or smart functionality does not remove the need for mechanical security. Some smart products operate an existing certified cylinder/thumbturn; others replace part of the locking hardware. Check what component is actually providing thief resistance, how the door opens during power/battery failure and whether the product preserves safe egress. App convenience is not itself a security standard.

Buying Online: Avoid “Compatible With” Confusion

Online listings may say a lock is “BS compatible”, “insurance style” or “3-star type”. Those phrases are not substitutes for genuine certification. Check the exact model, standard number, current certificate/listing and markings you will receive. If the product page does not clearly state what has been certified, ask before buying.

A Standards-Based Door Assessment

When to Keep the Existing Lock and When to Upgrade

British Standard Locks: Final Verdict

For a suitable traditional timber entrance door, BS 3621 remains a key thief-resistance benchmark, while BS 8621 is the important keyless-egress counterpart. For a modern euro-cylinder door, TS 007 cylinder/security-hardware ratings are often more directly relevant, and PAS 24 matters when considering the tested security of a complete new doorset.

The best security decision is therefore to match the standard to the hardware and door, check the current revision/marking, preserve safe egress and follow your own insurer's wording. You can learn more about APEX Locksmith & Joinery before arranging an assessment.