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UK Standards Decoded

UK Door Lock Grades Explained

BS3621. BS8621. TS007 3-star. Sold Secure Diamond. EN1303. PAS24. Secured by Design. Every UK lock grade a homeowner or landlord actually needs to know, translated out of the technical jargon and into something you can act on before you buy.

Locksmith South London 14 min read Updated April 2026 Rated 5.0 on Google
60-Second Cheat Sheet

Every UK lock grade, in one glance

BS3621 — timber-door deadlocks, key both sides, insurer default since 1980.
BS8621 — same as BS3621 but exits on the internal handle. HMO & flat compliant.
TS007 1–3★ — Kitemark stars for euro cylinders & handles; 3★ is the benchmark.
Sold Secure SS312 — Bronze/Silver/Gold/Diamond, MLA-owned, Diamond ~ TS007 3★.
EN1303 — European cylinder grading, 8-digit code covering key security & attack.
PAS24 + SBD — whole-doorset tests + police-preferred badge for the complete assembly.
In This Guide

13 chapters covering every UK lock grade

Jump to the grade you need. Each chapter covers what it tests, who requires it, how to spot it on a lock, and which brands carry it.

01Why grades matter (and who invented them) 02The 7 UK grading families at a glance 03BS3621 — the timber-door standard 04BS8621 & BS10621 — escape & containment 05TS007 — the star rating system 06Sold Secure SS312 — Bronze to Diamond 07EN1303 — the European 8-digit code 08PAS24 — the whole-doorset test 09Secured by Design (SBD) 10Grade cross-reference table 11What UK insurers actually require 12How to identify a grade on your lock 13Frequently asked questions
Chapter 01 — Why Grades

Why grading exists — and why it finally matters in 2026

A lock without a grade is a claim waiting to be refused. Every major UK home insurer now names a specific standard in the security clause of their policy. Miss the standard and a burglary claim can be reduced or denied outright, however much you paid for the lock.

Grades exist because "this lock is secure" stopped being a useful statement roughly forty years ago. As forced-entry techniques evolved — snapping, bumping, picking, drilling, kicking — the industry needed a shared yardstick so an insurer in Bristol and a locksmith in Bromley could agree on whether a specific lock was fit for purpose. The British Standards Institution (the people who stamp the Kitemark) wrote the first one in 1980, and the system has been expanded, cross-referenced and argued over ever since.

You'll meet seven different grading families in this guide. That sounds overwhelming but they mostly answer a different question: does the lock resist attack (BS3621, TS007, Sold Secure)? Does it exit safely in a fire (BS8621)? Does the whole doorset survive a rugby kick (PAS24)? Is the key genuinely hard to copy (EN1303)? Once you understand which question each grade answers, choosing a lock becomes a three-minute job instead of a Saturday afternoon.

If you're early in the decision and haven't picked a door type yet, read our how to choose a door lock guide first. For full ranked brand picks, see the best door locks UK comparison, and to talk through your specific policy wording, our South London engineers offer a free security audit — send us a photo and a mention of your insurer. We've been grading and fitting UK locks since 2015.

Chapter 02 — Grade Families

The 7 UK lock grade families at a glance

Each grading family answers a different question. This is the overview — the deep dives follow from Chapter 3 onward.

Attack resistance

BS3621

British Standard — timber

Does the lock body resist picking, drilling and prising?Key-operated both sides, 5-lever minimum, 3-minute attack test.

BSI Kitemark
Fire escape

BS8621

British Standard — escape

Can someone inside exit without a key during a fire?Handle-operated internally, key-operated externally.

BSI Kitemark
Snap resistance

TS007

Kitemark stars — 1–3★

Does the euro cylinder resist snap, drill, pick, bump?1-3 stars applied to cylinder and/or handle furniture.

DHF / GGF
Independent test

SS312

Sold Secure — Diamond

Does the product survive extended specialist-tool attack?Bronze/Silver/Gold/Diamond tiers, MLA-owned body.

Sold Secure (MLA)
Key control

EN1303

European cylinder — 8-digit

How hard is the key to copy? How long does the cylinder last?Key security 1–6, attack 0–2, durability, fire.

CEN (EU)
Whole doorset

PAS24

Publicly Available Spec

Does the entire door assembly resist attack, not just the lock?3-minute combined attack + forced entry tests.

BSI publication
Police badge

SBD

Secured by Design

Has UK police design-out-crime team approved this product?Overlay badge on products that already meet above.

UK Police
Padlock spec

EN12320

European padlock

How much abuse can the padlock body take?Corrosion, temperature and attack grades 1–6.

CEN (EU)
Identifying a BS3621 Kitemark on a UK timber front door lock
Look on the lock faceplate for the BSI Kitemark and the engraving "BS3621".
Chapter 03 — BS3621

BS3621 — the British Standard that insurers still quote first

BS3621 is British Standard 3621, issued in 1980 and revised multiple times (currently BS3621:2007 + A2:2012). It is the UK's thief-resistant lock standard for timber final exit doors, and despite its age it's still the first standard most home insurers mention in the security clause of your policy.

It covers a narrow but important question: does the lock body itself resist a determined manual attack, with hand tools, for a defined period? The testing regime puts the lock through picking, drilling, sawing, prising and bumping attempts by two accredited testers inside a laboratory setting.

What BS3621 requires

  • Key-operated from both sides — no internal thumb-turn
  • Minimum 5 levers with at least 1,000 different key combinations
  • Hardened bolt — 20mm+ throw, anti-saw protection
  • 3-minute manual attack resistance — the average UK burglar gives up within this window
  • Anti-drill pins within the keyway and hardened faceplate

Who needs BS3621?

Almost every UK home insurer requires BS3621 (or a Kitemarked equivalent) on "final exit doors" — the front door, any back door, and any door from an attached garage. If your policy document mentions "British Standard" or "5-lever deadlock" in the security clause, this is what it's referring to. Brands commonly specified: Union 2134E, Chubb 3G114, ERA Fortress, Yale PM552. Full brand breakdown on our 5-lever mortice page.

Chapter 04 — Escape & Containment

BS8621 & BS10621 — when BS3621 isn't the right answer

Two lesser-known members of the BS family cover scenarios where the basic "key both sides" rule of BS3621 becomes a problem.

Fire-escape variant

BS8621 — key out, handle in

BS8621 is the thief-resistant plus escape cousin of BS3621. It meets the same external attack criteria but swaps the internal keyhole for a handle that always operates from inside.

This is essential in any property where a key might not be immediately available during a fire:

  • HMOs and multi-tenancy properties
  • Flats and communal-access buildings
  • Student housing, elderly-care & rented homes
  • Any Fire Safety Order 2005 compliant door
Use on: HMOs, flats, rented timber doors
High-security variant

BS10621 — lockable from inside

BS10621 extends BS3621 with a user-controlled internal lock override. When engaged, the door cannot be opened from the inside even with a key — blocking a burglar who has entered from making an exit with your goods, and stopping "bump and drag" raids in flats.

This trade-off has real fire-safety implications and isn't for every home:

  • High-risk postcodes with persistent burglary
  • Holiday homes and empty properties
  • Secondary doors where fire-exit isn't required
  • High-value property on insurance schedules
Use on: high-risk / unoccupied homes
Chapter 05 — TS007

TS007 — the star system for euro cylinders

BS3621 doesn't work on a uPVC door because there's no mortice pocket. TS007 (Technical Specification 007) was introduced in 2011 specifically to certify euro cylinders against the snapping epidemic. It's a Kitemarked star rating applied to two separate components — the cylinder and the handle/escutcheon — and it adds up.

★
1★
Basic

Entry-level certified cylinder. Needs a 2-star handle over it to reach insurer-acceptable protection. Alone, only suitable for internal or low-risk doors.

★★
2★
Security handle

Applied only to handles, escutcheons and furniture. Stops the cylinder being pulled, bored or levered externally. Pairs with a 1-star cylinder.

★★★
3★
Cylinder — standalone

Stands alone — no supplementary handle needed. Passes snap, drill, pick and bump tests. The insurance benchmark for uPVC and composite doors.

The TS007 formula insurers accept

3-star cylinder alone   OR   1-star cylinder + 2-star handle = 3-star equivalent

Both reach the same tested tier. The second option is cheaper on paper but requires both components from compatible brands — easier to get wrong in DIY fitting. See our full anti-snap guide for brand-by-brand TS007 ratings.

Chapter 06 — Sold Secure

Sold Secure SS312 — the MLA's independent grading

Sold Secure is a UK testing body wholly owned by the Master Locksmiths Association. It sits independently of BSI and the DHF/GGF consortium behind TS007, and deliberately tests products against the real tools found on UK burglars — not a sanitised laboratory toolkit.

Its door-cylinder standard is SS312 Diamond (often just called "Sold Secure Diamond"). Products are awarded one of four tiers:

  • BronzeBasic tools — opportunistic attack only
  • SilverEnhanced tools — suitable for sheds & garages
  • GoldDedicated tools — mid-tier insurance acceptance
  • DiamondSpecialist tools — equivalent to TS007 3-star

Most UK insurers accept Sold Secure Diamond as equivalent to a TS007 3-star cylinder on uPVC and composite doors. Premium cylinders like the Ultion WXM and Avocet ABS Quantum carry both marks. Sold Secure also grades padlocks, chains, safes and bike locks, so you'll see the shield logo well beyond front-door cylinders — it's the same tier system across the board.

Gold grade padlock symbolising the Sold Secure Gold tier
Sold Secure tiers reach up to Diamond for the highest mechanical grade.
Chapter 07 — EN1303

EN1303 — the European 8-digit cylinder code

Flip a decent euro cylinder over and you'll often see a string of digits. That's EN1303, and each digit tells you something specific about how the cylinder performs.

1 · 6 · 0 · 0 · 1 · B · 0 · 2
Digit 1

Category of use — 1 = domestic, 2 = light commercial, up to 4 for heavy commercial. Higher = more daily cycles tested.

Digit 2

Durability cycles — 6 = 100,000 cycles. That's 15+ years of daily use.

Digit 3

Door mass — usually 0 (not applicable) for cylinders; applies to the mortice case on mortice locks.

Digit 4

Fire rating — 0 = not tested, 1 = suitable for fire doors.

Digit 5

Safety — 0 usually, irrelevant for cylinders.

Digit 6

Corrosion & temperature — A/B/C/D grades, B is standard.

Digit 7

Key security — the most important digit. Scale 1–6. A modern patented cylinder is 5 or 6.

Digit 8

Attack resistance — 0 = not tested, 1 = basic, 2 = enhanced. Digit-2 cylinders resist drill, pick and bump attacks.

Chapter 08 & 09 — PAS24 & SBD

PAS24 and Secured by Design — beyond the lock body

The previous grades test components. PAS24 tests the whole doorset. Secured by Design is a police overlay badge for products that already meet one of the above.

Whole doorset

PAS24:2022

Publicly Available Specification

PAS24 is BSI's specification for enhanced security doorsets — door, frame, hinges, lock and glass as one tested assembly. Mandatory in most new-build planning and on many Housing Association schemes.

Tests include manual attack tools, cylinder snapping, and a 3-minute forced-entry window.

  • Kitemark required on the cylinder
  • Tests frame, hinges & glazing together
  • Mandatory for new-build homes
  • Typical fit: composite & insurance-approved doorsets
Police badge

Secured by Design

UK Police Official Security Initiative

Secured by Design (SBD) is run by National Police Chiefs' Council and awards a badge to products that already carry TS007, BS3621 or equivalent. It's an overlay — confirmation that the police crime-prevention team has reviewed and approved the product.

Often influences housebuilder specifications and some HOA schemes.

  • Requires underlying Kitemark or equivalent
  • Badge on packaging & paperwork, not stamped
  • Useful for housebuilder & local authority specs
  • Common on Avocet ABS, Yale Platinum, Ultion
Chapter 10 — Cross-Reference

UK lock grades, cross-referenced

Use this single table as your reference. It shows each grade's applicability, insurer acceptance and real-world equivalent at a glance.

Grade Applies to Tests for Insurer accepts Equivalent
BS3621TimberManual attack, picking, drillingYes — industry default— baseline
BS8621Timber, HMOBS3621 + internal handle escapeYes — HMO & flat requiredBS3621 + escape
BS10621Timber, high-riskBS3621 + internal lockoutYes — premium schedulesBS3621 + containment
TS007 1★uPVC cylinderBasic cylinder attackOnly with 2★ handleSold Secure Bronze
TS007 2★Handle / escutcheonPull, bore, lever protectionOnly paired with 1★ cylinderSold Secure Silver (furniture)
TS007 3★uPVC / compositeSnap, drill, pick, bumpYes — standaloneSold Secure Diamond
SS312 DiamondCylinderSpecialist-tool attackYes — TS007 3★ equivalentTS007 3-star
SS GoldPadlock / chainDedicated-tool attackMid-tier policiesTS007 2-star-ish
EN1303 1–6European cylinderKey security & durabilityOnly with TS007 / SS312 add-onNot a primary grade
PAS24Whole doorsetCombined 3-minute attackBonus signalPAS24 + TS007 = premium
Secured by DesignAny certified productPolice-preferred overlayYes — bonus badgeLayered on BS3621 / TS007
EN12320PadlocksCorrosion, attack, temperatureShed / outbuilding policiesSold Secure Bronze+
Chapter 11 — Insurance

What UK insurers actually require

Policy wording varies but the same three scenarios cover 95% of UK home insurance clauses. Find yours below and note the specific grade requirement.

Scenario 01

"Locks conforming to British Standard 3621"

The classic clause. Found on Admiral, Aviva, Direct Line, LV=, Churchill, NFU and most mid-market policies.

Requires a BS3621 (or BS8621/BS10621) mortice deadlock on all final exit doors. On uPVC without a mortice pocket, most insurers will accept TS007 3-star or Sold Secure Diamond in writing — confirm by email.

Scenario 02

"Kitemarked equivalent approved in writing"

The flexible clause. Found on Hastings, esure, Halifax, Admiral Gold, and most new-build-targeted policies.

Accepts TS007 3-star, Sold Secure Diamond, or BS3621 interchangeably. The "approved in writing" phrase means call or email the insurer before buying and keep the confirmation on file.

Scenario 03

"5-lever mortice deadlock"

The narrow clause. Older policies, some landlord policies and a handful of building-society-tied ones.

Only specifies BS3621 mortice locks. Won't accept TS007 cylinders even on uPVC. Switch insurer at renewal if you have a modern door.

Rule of thumb: save a written email from your insurer confirming acceptance before fitting. On renewal, most insurers reduce premium by 5–15% when you upload a locksmith's written specification showing BS3621 or TS007 3-star compliance. We include that paperwork free with every insurance-approved lock fit.

Chapter 12 — Identification

How to identify the grade on your existing lock

Five places to look, in order of priority. A torch, a phone camera and five minutes — everything you need to confirm or rule out compliance.

01

Open the door and look at the edge

The lock faceplate is the metal strip along the door edge where the bolt comes out. It should carry an etched BSI Kitemark and a standard number (e.g. BS3621). Etched = certified. Sticker = suspicious.

02

Check the bolt itself with a torch

Slide the bolt out by turning the key. Look along the bolt body for engraved text. BS3621 mortice bolts often have "BS3621" or the Kitemark stamped into the side of the bolt.

03

Inspect the euro cylinder (uPVC/composite)

Look at the visible cylinder body between the key and the door edge. TS007 cylinders carry a small Kitemark and 1, 2 or 3 stars. Sold Secure products show a shield logo and "Diamond". No marks = unrated = replace.

04

Read the EN1303 code

On the back of the cylinder or along the edge, look for an 8-digit code. The last two digits are what matter for security — digit 7 is key security (aim for 5 or 6), digit 8 is attack resistance (aim for 2).

05

Photograph and compare

Photograph each of the above and search the brand + code online. If you can't find proof of certification, assume not certified. Or just send us the photo via WhatsApp — we'll identify it in under an hour.

Locksmith South London Expert Tips

Grade-buying shortcuts from the van

Four rules that save customers from over- and under-buying on grades every week.

  • Screenshot the policy page

    Before you shop, screenshot the security clause of your insurance policy. Most clauses are hidden on page 22 of a 40-page PDF. One screenshot on your phone prevents the £300-then-swap-it mistake we see every week.

  • Don't chase Diamond if Gold will do

    Sold Secure Diamond on every door is theatre. Diamond on the front, Gold on the side, a Silver padlock on the shed — each grade matched to its actual threat model. Over-buying a grade just means you leave less budget for other doors.

  • Kitemark alone means nothing

    The Kitemark is a logo, not a standard. It tells you the product was independently tested — but for what? Always read the standard number next to the Kitemark (BS3621, TS007, PAS24). A Kitemark with no standard is worthless.

  • Keep the proof

    Every certified lock we fit leaves with a printed spec sheet from our engineer. Clip it to the inside of your meter cupboard. The day you need to claim or renew insurance, that paper is the difference between a 10-minute process and a three-week dispute.

Customer Reviews

South London upgrades — before and after the grade change

Real customers who sent us a photo of their existing lock first. Rated 5.0 on Google.

Insurance letter said I needed BS3621 but I couldn't find a Kitemark on anything. Yusuf came round, photographed each door, confirmed my existing mortice was actually a 3-lever (not compliant). Union 2134E fitted next day with the spec sheet for the insurer. Smooth process start to finish.

YI
Yusuf I.Brixton, SW9 — Union 2134E BS3621

Landlord of a 6-bed HMO, needed BS8621 on every flat door for the fire risk assessment. Team did the whole block in two days, all keyed to a master system so I hold one key for emergency access. Every lock shipped with the Kitemark paperwork for council inspection.

AM
Adesh M.Peckham, SE15 — BS8621 HMO refit

New-build composite door came with what the developer called a "high security cylinder". Asked the team to check — turned out it was 1-star, couldn't see that on the packaging. Swapped for an Ultion WXM Diamond + TS007 3-star for £220 fitted. Proper paperwork this time.

EP
Emma P.Crystal Palace, SE19 — TS007 3-star upgrade
Chapter 13 — FAQ

Lock grade questions we answer on the phone every week

Quick answers to the grade questions UK homeowners keep asking. Cross-referenced to the chapters above.

What lock grade does my UK insurance need?

Most UK home insurers require BS3621 on timber final exit doors, and accept TS007 3-star or Sold Secure Diamond cylinders on uPVC and composite doors.

Check your policy wording — any mention of "British Standard", "BS3621" or "Kitemarked" means a certified lock is mandatory, not optional. See Chapter 11 above for the three common scenarios.

Is TS007 3-star the same as Sold Secure Diamond?

They are broadly equivalent on euro cylinders — both are tested against snap, drill, pick and bump attacks, and most UK insurers accept either for uPVC and composite doors.

TS007 testing uses a 3-minute protocol; Sold Secure Diamond uses a longer window but heavier tools. In practice, premium cylinders like Ultion WXM and Avocet ABS carry both marks.

What is the highest door lock grade in the UK?

For timber doors: BS10621 is the highest mechanical tier (BS3621 + internal lockout). For uPVC and composite: a TS007 3-star cylinder + Sold Secure Diamond + a Secured by Design approved handle set on a PAS24 doorset is the highest combined grade available.

How do I tell which grade my existing lock has?

Open the door and torch the edge of the lock. BS3621 locks have a BSI Kitemark stamped on the faceplate and "BS3621" engraved on the bolt. TS007 cylinders show a small Kitemark logo plus 1, 2 or 3 stars. Sold Secure locks carry a shield logo labelled Bronze, Silver, Gold or Diamond.

No marks = no certification. Chapter 12 above has the full step-by-step.

What is the difference between BS3621, BS8621 and BS10621?

BS3621 is the baseline — key-operated both sides, thief-resistant. BS8621 adds handle-operated escape from inside (HMOs, flats, fire exits). BS10621 lets the user lock the internal handle so a burglar inside can't exit with goods — highest mechanical tier but with fire-safety trade-offs.

See our BS3621 guide for practical examples.

Does a Kitemark alone mean my lock meets BS3621?

No. A Kitemark only means the product has been independently tested — the specific standard it was tested against is what matters.

Always look for the standard number beside the Kitemark (e.g. "BS3621", "TS007 3-star"). A Kitemark on its own is meaningless for insurance. That detail is what gets customers claims denied.

Are Sold Secure grades recognised by UK insurers?

Yes. Sold Secure Diamond is widely accepted as equivalent to TS007 3-star on cylinders, and Sold Secure Gold meets most standard policies for padlocks, chains and shed locks.

Always confirm with your insurer in writing — some specify BS3621 only, even when Sold Secure is more secure. Chapter 06 above explains the tier system.

Do smart locks have a lock grade?

Only the mechanical cylinder inside a smart lock carries a grade. The electronics themselves are not graded under the standards in this guide.

That's why we only recommend smart locks built around a TS007 3-star or Sold Secure Diamond mechanical core — the electronic part adds convenience but the physical cylinder does the security lifting.

Keep reading

Related guides & lock pages

Go deeper on any grade above — every link is a proper in-depth page on our site.

Standards

BS3621 Locks & Insurance

Kitemark identification, insurance clauses, and the 5-lever deadlock pattern to specify.

Read guide Blog

Best Door Locks for Home Security UK

Ranked 2026 buyer's guide with the top 5 cylinders and mortice brands and their grades.

Read guide Blog

How to Choose a Door Lock UK

The 7-step locksmith method — matches grade to door, insurance and budget.

Read guide

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5-Lever Mortice Lock BS3621 Locks British Standard Explained Euro Cylinder Lock Anti-Snap Locks Anti-Snap Cylinder Insurance Approved Locks Types of Door Locks uPVC Door Locks Composite Door Locks Wooden Door Locks Smart Door Locks

South London areas we cover

Croydon CR0 Sutton SM1 Wallington SM6 Purley CR8 Coulsdon CR5 Thornton Heath CR7 South Croydon CR2 Norbury SW16 Sanderstead CR2 Kenley CR8
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