Will Locksure fit my lock?

Locksure fits most euro cylinder locks with a thumb turn or a key on the inside of the door. It is not a universal fit, so take two minutes at your door before you order. Four quick checks tell you almost everything. If you are still unsure, send us a photo and we will check it for you before you buy.

The four checks (thumb turn) and three checks (key turn)

1. A flat lock plate. The plate (escutcheon or handle backplate) around the cylinder must be flat, not curved or domed. The monitor sticks to this plate with adhesive, so it needs a flat surface to grip.
2. More than 34 mm of flat space below the barrel. Measure from the bottom of the cylinder barrel to the bottom edge of the lock plate. You need more than 34 mm of flat plate for the monitor body to sit on.
3. The barrel stands proud by at least 1 mm. Lay a coin flat across the cylinder. If the coin sits on the barrel and clears the plate, you have enough. If the barrel is flush with the plate, or recessed, the monitor cannot locate on it. Spacers and brackets in the box take up a barrel that protrudes up to about 6 mm.
4. Thumb turn only: room for the magnet. The small turn-sensing magnet sits on the thumb turn rod between the end of the barrel and the thumb turn head. Two 10p coins stacked (about 4 mm) must fit in that gap.

Passes every check? It will fit. For a key turn door, repeat checks 1 to 3 on the outside of the door as well, because the Key Turn pack puts a monitor on each side.

What does the door material matter?

Much less than people expect. UPVC, composite, aluminium and timber doors all work, because the monitor attaches to the lock plate, not the door. What matters is the lock: a euro profile cylinder on a flat plate, with the barrel slightly proud. Door thickness does not matter either, as long as the cylinder has been fitted so it protrudes a little on the inside.

Which locks do not fit?

• Mortice deadlocks (the five-lever “BS3621” lock with a keyhole and no cylinder, common on older timber doors).
• Rim nightlatches (the Yale-type box lock on the inside face of the door).
• Curved, domed or rounded escutcheons and handles with a shaped backplate: there is nowhere flat for the adhesive.
• Cylinders that are flush or recessed behind the plate. A locksmith can often swap the cylinder for one 5 mm longer on the inside, which solves it, but check with us first.
• Handles whose body covers the cylinder (an integrated or “inline” handle with the keyhole inside the handle casting).
• Fob, card or keypad systems with no turning cylinder.

Other cylinder shapes, and thumb turns with unusually large or decorative heads, are worth a photo check before you order.

Thumb turn or key on both sides?

Look at the inside of the door. A small knob you turn by hand is a thumb turn: choose the Thumb Turn monitor (one sensor, fitted inside). A keyhole on both sides is a key turn, sometimes called a double euro cylinder: choose the Key Turn pack (two sensors, one each side). Not sure what you have? See Which lock do I have?

Renting?

The monitor attaches with adhesive and nothing is drilled. It is still worth checking your tenancy agreement, and the removal cord in the box takes it off cleanly when you move out. See Removing Locksure or moving house.

Still not sure? Send a photo

Use the Ask Locksure form and attach one clear photo of the inside of your door showing the handle, the cylinder and the space around it (both sides for a key turn). Tell us which side the photo shows. We will reply by email and tell you which monitor fits, or say honestly if it will not.

Once you know it fits, see Matter or Original: which should I buy? or go straight to the Thumb Turn Starter Pack or Key Turn Starter Pack.

Questions people ask about fit

Does it fit a UPVC door?

Yes, if the lock is a euro cylinder on a flat plate and passes the checks above. Most UPVC doors do.

Does it fit a composite door?

Usually yes. Composite doors nearly always use a euro cylinder. Check the plate is flat and the barrel is at least 1 mm proud.

Does it fit a wooden door?

If the door has a euro cylinder with a flat escutcheon, yes. If it has a mortice deadlock with a plain keyhole, no.

My cylinder is flush with the plate. Can I still use it?

Not as it is. A locksmith can usually fit a cylinder that is 5 mm longer on the inside, which gives the monitor something to locate on. Send us a photo first and we will advise.

Do I need to change my lock?

No. Locksure reads the position of the lock you already have. The cylinder, keys and the lock’s security rating stay as they are.

Back to the Help Centre