The warning signs a lock gives before it fails

The key needs persuading

Jiggling, lifting slightly, pushing in and easing back a fraction — all of it means the pins are no longer meeting the key cuts cleanly. Either the cylinder is wearing, or dust and old lubricant have built into a paste.

This is the earliest stage and the most fixable. Cleaned and correctly lubricated here, most cylinders carry on for years. Ignored, the extra force you apply each time is what eventually snaps a key.

The handle needs a second go

On a multipoint lock the handle throws several bolts at once. If it only engages on the second attempt, the bolts are not meeting their keepers squarely — which is the door or the frame, not the lock.

This one is worth acting on quickly. The gearbox inside a multipoint mechanism is what eventually fails under repeated force, and a gearbox is one of the few components where replacement genuinely is the only route. Adjusting keepers is cheap by comparison.

It only works in one position

If the lock behaves with the door open but not closed, or only at a particular point in the swing, alignment is marginal and the mechanism is working under load it was not designed for. Same cause, same fix, same consequence for leaving it.

Grey dust on the key

Look at the key after use. Fine metal powder means the internals are wearing against each other. Dust gets into cylinders through summer and the first heavy rains turn it into an abrasive paste.

Once wear is visible on the key itself, the cylinder is on borrowed time.

A key that has started to bend

Check where the blade meets the head. A key fighting a stiff lock work-hardens at that point until it fails, usually with no warning and usually inside the lock.

A tired key is evidence about the lock. Replacing the key alone just restarts the same clock.

Outdoor hardware, checked separately

Security gates, pedestrian gates and outbuilding locks live in weather and dust and get used far less often, so they seize rather than wear. Nobody notices until the day they need them.

If a technician is already on site, having those checked at the same time costs very little and prevents the classic estate lockout where the front door is fine and the gate is not.