The key goes in with a faint crunch. It turns, but not smoothly, and some days you have to wiggle it. If the door is anywhere near the beach in Guardamar, the most likely cause is sand.
This is a town that was nearly buried by its own dunes. In 1896 they started moving into the north of the town, and it took more than thirty years of reed fences, grasses and some 600,000 pines, the pinada we walk through today, to hold them. They are held, but the sand still blows, and the fine grains are small enough to ride into a keyhole.
Why sand jams a cylinder
Inside a cylinder are small spring-loaded pins. The key lifts each one to exactly the right height so the plug can turn. A grain of sand under a pin, or wedged beside the plug, stops that happening, so the key turns partly, or only when wiggled, or not at all.
Three things that get the grit out
- Blow it out. A can of compressed air with a thin straw, into the keyway, several short bursts. Do it with the key out, then again after putting the key in and out a few times to loosen grit.
- A dry lubricant. A graphite powder or a PTFE dry spray made for locks, a small puff into the keyway. Put the key in and turn it several times to spread it.
- Clean the key. Grit on the key goes straight back into the lock. A toothbrush and a dry cloth.
Three things that make the grinding worse
- Oil, grease or general-purpose sprays. They wet the sand and turn it into a paste that holds every grain where it is, and catches the next ones. After a summer it is like mortar.
- Forcing the key. Most keys that snap inside a lock snap because somebody turned harder. A broken key in a sandy cylinder means extraction, and often a new cylinder.
- Pliers on the key. Twisting with pliers bends the key and the pins.
When it is past cleaning
If after cleaning the key still has to be wiggled, the pins themselves are worn. Salt air on a door facing the sea speeds that up. A worn cylinder only gets worse and tends to fail on the worst possible day, so the sensible thing is to replace it on a day of your choosing.
Sand also gets into the tracks of terrace doors; that has its own guide. For a house that sits shut through the winter, read three homes in four stand empty. If the key has already broken off and you are outside, it is a job for opening the door first.