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How To Fit A Lock & Advice On Choosing A Lock Replacement

How To Fit A Lock & Advice On Choosing A Lock Replacement
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Ensuring that your house is safe and secure is one of the most important things you can do. Our experts have put together this handy home security guide to help you choose and install a new lock without the need for a locksmith.

Changing door locks can be a tricky task so will suit you if you’re experienced in DIY, or simply enjoy a challenge.

Before you get started on any of our ‘how to’ guides or a project that requires power tools, please take a moment to read through our DIY safety tips.

What You'll Need:

How to choose a new lock

The more levers, pins or discs a lock mechanism has, the more difficult it is to pick. Look for locks that have features like anti-pick, anti-drill, and anti-bump mechanisms. Additionally, consider locks made from strong materials like solid brass or stainless steel for added strength and resistance against tampering. The main locks on your exterior doors should be to BS3621 standard. Most insurance companies demand this level of security.

1. Look for the Kitemark

Ensure that you're getting a high-quality lock by looking for the Kitemark. The Kitemark is a symbol of quality and safety, indicating that the lock has been tested and meets the necessary standards (British Standard BS3621). Most insurance companies will insist that you have these, and they’re recommended by crime prevention officers too.

kitemark symbol

2. Front door

When possible, fit two locks on your front door – both to BS3621 standard. Position a mortice deadlock about halfway up the door (usually just below the door handle) and fit a night latch on your front door one-third of the way down. If you only fit one lock, go for an automatically dead-locking night latch made to BS3621 standard.

3. Back door

Protect your back door with a mortice sash lock to BS3621.

4. Bolts and additional security

It’s a good idea to fit hinge bolts, especially to doors that open outwards, as the hinge knuckle pins are a weak point. Position them 150mm below the top hinge and 150mm above the bottom hinge. Strengthen your back door with security mortice bolts, following the manufacturer’s instructions for installation guidance.

Top tip: When drilling for the mortice recess, use a piece of tape on your drill bit to mark how deep you should drill each time.

How to change a door lock

Below you'll find information on the four most common types of lock and how to install them correctly and securely.

Mortice deadlocks and mortice sash locks

Mortice deadlocks are usually found on front doors. They are fitted into the edge of a door, allowing it to be locked manually from both the inside and outside. The term 'deadlock' simply means that once the key is removed, the lock will remain locked or unlocked until the key is manually inserted again.

Mortice sash locks are also fitted into the edge of the door, though they are more commonly found on back doors and internal doors. A sash lock consists of a non-locking latch, a deadlock and a handle or knob mechanism that works on both sides of the door.

Whether you have a mortice deadlock or sash lock, the installation process remains the same.

Don’t fit the lock at the rail joint as this will weaken the door. Position it about halfway up the door where the timber is solid.

Hold the door in the open position and use either the manufacturer’s template (if supplied) or the body of the lock to mark the mortice’s position on the edge of the door.

Set a marking gauge to half the thickness of the door and score a line down the door edge to mark the position of the lock.

mark the mortice position on the door

Drill holes on this centre line the same width as your lock.

drill holes along this line the same width as the lock

Chisel away a small amount of wood at a time to open the drill holes into a clean rectangular hole to fit your lock.

chisel to open the drill holes into a clean rectangle

When the mortice lock space is chiselled out, insert the lock and outline the faceplate with a marking knife.

insert the lock and outline the faceplate with a knife

Chisel a recess for the faceplate. Then mark and drill screw holes to fix it in place.

chisel a recess for the faceplate

Use the lock body to mark the position for the keyhole.

mark the position for the keyhole

Use a drill and a thin-bladed pad saw to form the keyhole. Check the keyhole for fit from both sides of the door. Install the lock body and screw on the faceplate.

use a drill and thin-bladed pad saw to form the keyhole

With the bolt out and held against the door frame, mark the position of the striking plate and the depth of the bolt box. Use these marks to position the striking plate on the inside surface of the door frame.

mark the position of the striking plate and depth of the bolt box

Recess the plate into the door frame. Cut out the wood to receive the bolt. Drill holes for the recess plate screws.

drill holes for the recess plate screws

Before you fix the plate make sure the door closes properly. Fit the key plate over the hole and place the key in the lock with the key plate loose on the shaft of the key. Fix the key plate in place.

Finally, tighten terminal screws securely.

Night latches

A night latch is a spring lock that can be opened by key from the outside or from the inside with a small handle or knob. They are usually found on front doors, often in addition to a mortice deadlock.

Read the manufacturer’s instructions before starting this job. Then, mark and drill the hole for the rim cylinder through the door stile about one-third of the way down from the top of the door.

where to fit locks on your door

The diameter and position for the hole will be in the manufacturer's instructions, usually shown as a template.

Place the slip ring B over the cylinder C and insert it into the hole in the door. Then place the fixing plate D over the hole. Secure it with connecting screws A, so the cylinder and fixing plate are upright.

fix together with the screws provided

If you haven't already done it, take the key out of the cylinder. Check the arrows on the thimble E and lock cover plate F line up.

Place the case I over the fixing plate, making sure connecting bar G enters the slot in thimble E. The connecting bar often needs shortening – you can do this with a hacksaw.

You might need to mark and cut the edge of the door if the lock cover plate F has a lip. Use a chisel for this.

Replace the case and fix screws H to attach the case to the door.

Line up the striking plate (the metal piece on your door frame that the lock bolt enters) with the lock bolt J. Mark its position on the door frame and chisel out the wood for a flush fit. Fix it in place with the screws provided.

Top tip: Make sure all your door frames are in good condition or they'll make your locks ineffective. If the frame can be moved or rocked when you push it, either add extra wall fixings, or replace or repair the frame.

Euro cylinder locks

Also known as a Euro lock barrel, a Euro cylinder locks are a common choice for uPVC doors. For strong security, always opt for a model with at least six pins.

Look for the latest security standard – BSEN1303:2005 – that tests against all methods of beating a lock. The cylinder also has Secured by Design accreditation – a police-preferred specification that focuses on crime prevention.

When choosing a Euro cylinder lock, consider the size and depth of your door. The cylinder only needs to be slightly longer than the depth of your door. If the cylinder protrudes too far from the surface of the door, it is easier to break off.

Rim cylinder locks

Most night latches are secured on the outside by a rim cylinder lock. Replacing a rim cylinder on an external timber door is an easy and effective way to secure your home without having to change the entire lock or door.

Upgrade to a British standard rim cylinder and you can be confident the lock been tested to withstand all known ways to break it.

With an understanding of the different types of lock and how to fit them, you're right on track to improving your home security.Share your own top DIY tips with us @Homebase_UK or take a look at our Ideas & Advice hub for some more home inspiration.

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