Choosing and Fitting a Reliable Door Lock

Why the Lock on Your Front Door Matters More Than You Think

Most burglaries in the UK are opportunistic. The intruder does not arrive with a drill and a plan; they try a handle, look for a weak point, and move on if the door holds firm. That means your lock is not just a piece of hardware — it is the single most important line of defence your home has. A cheap cylinder picked up from a discount bin can be snapped in seconds with a pair of mole grips, while a properly specified British Standard lock will send most casual intruders looking for an easier target.

The good news is that you do not need to spend a fortune or become a locksmith. You need to know what to look for, where to fit it, and how to keep it working properly. This guide walks you through all three.

Look for the Kitemark Before You Buy

When you are standing in a shop or scrolling through listings, the easiest quality filter is the British Standard Kitemark. A lock carrying BS 3621 has been tested against a realistic set of attack methods, including picking, drilling and forced entry, and has met a recognised minimum standard for a thief-resistant lock. For external doors, this is the benchmark to aim for.

You may also come across BS EN 1303, which grades cylinders on a scale from one to six for key security, attack resistance and durability. A cylinder rated three stars offers good resistance to snapping and picking. Where possible, choose a lock that carries both the BS 3621 Kitemark and a solid BS EN 1303 rating — that combination tells you the product has been independently assessed rather than simply marketed well.

• Check for a visible Kitemark on the packaging or the lock body itself.
• Prefer locks rated to at least BS 3621 for final exit doors.
• Look for a three-star cylinder rating where the lock uses a euro profile.
• Be wary of unbranded locks with no certification at all.
• Keep the fitting instructions — insurers sometimes ask for proof of specification.

Fit a Deadlock to Every External Door

A spring latch alone is not enough. It can often be slipped with a piece of plastic or a thin blade. A deadlock throws a solid bolt that cannot be pushed back once engaged, and this is the type of lock you want on all external doors, including the back door, side gate and any door leading into a garage or conservatory.

For a timber front door, a five-lever mortice deadlock to BS 3621 is a traditional and very robust choice. For uPVC and composite doors, a multipoint locking system with a euro cylinder is standard, and here the quality of the cylinder is what matters most. If your door already has a multipoint mechanism, you can usually upgrade just the cylinder rather than replacing the whole lock.

Fit the lock roughly a third of the way up the door, away from any glass panels. If there is a letterbox or a cat flap nearby, make sure nobody can reach through and turn a thumbturn from the inside. Where a door has glass within arm's reach of the lock, consider a key-operated lock on both sides rather than a thumbturn, and keep the key well away from the door when the house is empty.

• Use a five-lever mortice deadlock on timber external doors.
• Upgrade the cylinder on uPVC and composite doors rather than the whole mechanism.
• Position the lock away from glazing and letterboxes.
• Check that the bolt engages fully into the keep, with no rattle or play.
• Fit a door chain or limiter as a secondary measure for answering the door.

Spare Keys and Everyday Habits

Where you keep your spare key matters as much as the lock itself. A key under the mat, beneath a plant pot or on a string behind the letterbox is the first place an intruder will look, and some insurers will refuse a claim if a key was left in an obvious hiding place. Instead, leave a spare with a trusted neighbour, a nearby family member, or a friend you can call in an emergency.

If you must keep a key outside, use a wall-mounted key safe with a combination that is changed regularly and not shared widely. Never leave a key in the lock on the inside of an external door — it can sometimes be turned from outside through a letterbox or a broken pane.

It is also worth remembering that locks wear out. If your key is becoming stiff, if the bolt no longer throws smoothly, or if the cylinder feels loose, address it before it fails. A drop of graphite powder or a dedicated lock lubricant once or twice a year will keep the mechanism moving freely without attracting grit the way oil does.

Upgrading an Older Lock Without a Full Replacement

You do not always need to replace an entire lock. On euro profile cylinders, swapping the cylinder for a snap-resistant, anti-pick, anti-bump model is a straightforward job and gives a big jump in security for a modest cost. Look for cylinders that protrude no more than 3mm from the door handle backplate — anything longer gives a thief more to grip.

If your door has no deadlock at all, a surface-mounted deadlock is a reasonable retrofit for a shed or garage, but for a home's main entrance, a mortice or multipoint system is the better long-term answer. If you are unsure which type suits your door, a qualified locksmith can advise and fit the correct option in an hour or two.

Make Security a Habit, Not a One-Off Job

A good lock only works if you use it. Double-lock the door at night and whenever you leave the house, even for a short trip to the shops. Close and lock windows on the ground floor, and do not leave a back door unlocked while you are in the garden. Chain and padlock any side gates, and keep tools and ladders locked away so they cannot be used to help someone climb in.

Finally, take five minutes to check your locks this weekend. Look for the Kitemark, test the bolt, jiggle the handle to see if there is play, and make sure every external door has a working deadlock. It is a small amount of effort that pays back every single night you sleep soundly behind a door that will not give way.