WHAT THE GUIDANCE SAYS

Lock it,
and lock it well.

Most break-ins come through a door.

In England and Wales, three in four burglaries where the burglar got in were through a door, and a quarter of those doors were not locked. A good lock only works when it is turned.

LOCKED is the first defence

Check your lock

A painted front door of a terraced house in soft morning light, with a brass letterbox and a hand turning a key in the lock — AI-generated image, not a photograph of a real person or place.

Turn the key every time
Look for the standard
Keys away from the door
Small habits, safer homes

THE SHORT ANSWER

Lock up, and
check the mark.

A lock is only as good as its standard
and the habit of using it.

HOW IT WORKS

Pins on a line

In a pin tumbler lock, spring-loaded pins block the plug from turning. The right key lifts each pin so the gaps line up and the plug can rotate.

How locks work

uPVC DOORS

Lift, then turn

Secured by Design notes that locking a uPVC door means lifting the handle and turning the key, which puts several locks into place.

Check your lock

HABITS

Turn the key

In the latest Crime Survey figures, about a quarter of burglaries where a door was used involved a door that was not locked.

See the numbers

A QUICK LOCK CHECK

What is on
your door?

Pick the lock that matches your door to see what police guidance says about it. The bar shows how well it meets that guidance.

Lock check

Choose your lockDoor shut but not lockedCylinder lock with no star ratingTS 007 3-star or Sold Secure Diamond cylinder5-lever mortice deadlock to BS 3621

Door shut but not lockedNo barrier

An unlocked door was the way in for about a quarter of door burglaries in the Crime Survey for England and Wales. On a uPVC door, lift the handle and turn the key.

Cylinder lock with no star ratingConsider upgrading

Cylinder locks are on most uPVC doors, and West Yorkshire Police say some offenders have found ways to overcome them. A Master Locksmiths Association locksmith can advise.

TS 007 3-star or Sold Secure Diamond cylinderPolice minimum met

West Yorkshire Police call a 3-star solution the minimum to aim for. A 1-star cylinder with a 2-star handle also counts, and the cylinder should not stick out from the door.

5-lever mortice deadlock to BS 3621Standard met

Metropolitan Police advice for timber front doors is a 5-lever mortice deadlock with a boxed staple, conforming to BS 3621, about a third of the way up. Many insurers ask for BS 3621 locks.

Sources: West Yorkshire Police, Euro-cylinder advice; Metropolitan Police Service, How secure is your home? (2010); Lichfield District Council home security advice; ONS Nature of crime: burglary (year ending March 2025).

Based on West Yorkshire Police euro-cylinder advice and Metropolitan Police home security advice. This is general information, not a security survey.

TWO NUMBERS WORTH KNOWING

The easy way in
is often left open.

One figure on how burglars get in,
one on what tested security can do.

≈ 1 in 4

Door burglaries where the door was not locked

In the year ending March 2025, 76.9 percent of burglaries with entry in England and Wales used a door, and in 24.5 percent the door was not locked. The survey sample for that year was 128 incidents.

WAY IN · ONS CRIME SURVEY

42% fewer

Burglary fall on two Nottingham estates

After Secured by Design accredited windows were fitted to 1,520 homes, burglary fell by 42 percent, compared with a city-wide fall of 21 percent.

TESTED WINDOWS · SECURED BY DESIGN

ONS figures come from the Crime Survey for England and Wales, a household survey. The yearly sample of burglaries is small, so percentages can move from year to year: the unlocked-door share was 23.9 percent in the year ending March 2020.

FOUR HABITS TO TRY

Safer doors,
no new gadgets.

Most of these cost nothing. They come from police and Secured by Design advice for ordinary homes.

Lock it, even when you're in
A shut door is not a locked door. On uPVC, lift the handle and turn the key to throw every bolt.
Keep keys out of reach
Keep house and car keys away from the front door so they cannot be hooked through the letterbox.
Skip the hiding places
Avoid leaving keys under doormats, in fake rocks or above door frames.
Check the marks
Look for BS 3621 on mortice locks and TS 007 3-star or Sold Secure Diamond on cylinders.

A white uPVC back door seen from inside a kitchen, the handle lifted up and a key in the lock — AI-generated image, not a photograph of a real person or place.

A close-up of a cut brass key beside a lock cylinder on a wooden workbench, showing the jagged edge of the key — AI-generated image, not a photograph of a real person or place.

HOW A LOCK WORKS

Pins, springs
and one straight line.

Inside a pin tumbler lock, a plug sits in a casing. Each hole in the plug holds a key pin of a set length with a spring-loaded driver pin above it. Without the right key, the pins straddle the joint and the plug cannot turn.

The right key lifts every pair so each gap sits exactly on that joint, called the shear line, and the plug turns. The idea may date back to around 2000 BC in Egypt; Linus Yale Jr patented the design most modern locks resemble in 1861.

Questions

Questions people ask

What does BS 3621 mean on a lock?

It is a British Standard for locks. Metropolitan Police advice recommends a 5-lever mortice deadlock with a boxed staple, conforming to BS 3621, on timber front doors, and Lichfield District Council notes it is often required by home insurance policies.

What is a TS 007 3-star cylinder?

TS 007 is a rating for euro-cylinder locks and handles. West Yorkshire Police say a 3-star result is the minimum to aim for, either from a 3-star cylinder or a 1-star cylinder with a 2-star handle.

How do most burglars get in?

In the Crime Survey for England and Wales for the year ending March 2025, 76.9 percent of burglaries with entry were through a door and 19.8 percent through a window.

Why do I have to lift the handle on a uPVC door?

Secured by Design explains that locking a uPVC door requires the handle to be lifted when turning the key, which puts several locks into place.

Where should I keep my keys?

Police advice is to keep house and car keys away from the front door so they cannot be hooked out, and to avoid obvious hiding places such as under the doormat.

Lock it,
and lock it well.