Security Gate Lock Stuck or Key Won't Turn?

In short:

A security gate lock lives outdoors, so dust, rain and rust are the usual enemies. Many "stuck locks" are really a gate that has dropped or isn't closed properly.
One simple check tells you a lot: does the key turn freely when the gate is open? If yes, the problem is alignment, not the lock.
Don't spray lubricant into the keyhole unless the gate's maker says you may. Trellidor, for one, says not to.
Never force the key. A snapped key in a gate lock turns a repair into an extraction as well.
If the gate is under a maker's warranty, check its care terms before anyone works on it.

Why gate locks give trouble

The lock on your front door lives indoors, more or less. The lock on a security gate, burglar gate or trellis gate doesn't. It takes dust, rain and sun on the steel all year round. It's also attached to something heavy that moves: a hinged gate that can sag, or a retractable gate that has to be pulled exactly into place before the bolt lines up.

So when a gate key won't turn, there are really two suspects:

The gate: it has dropped on its hinges, has been knocked out of line, isn't fully closed, or the lock stile on a retractable gate isn't sitting where it should. The bolt is then pressed against the edge of the keeper and can't move.
The lock: dirt or corrosion inside, a worn or broken part, a worn key, or the wrong key.

The open-gate test

This is the most useful thing you can do yourself, and it doesn't involve taking anything apart. It only works if you can open the gate, of course; if you're locked out by it, skip to the section on calling for help.

Open the gate so the lock is clear of the frame or wall.
Try the key gently in both directions. Watch the bolt.
If the key turns smoothly and the bolt moves freely, the lock is probably fine. The trouble is in how the gate meets the keeper when it's closed.
If it's still stiff, gritty or won't turn with the gate open, the lock itself needs attention.

Illustration Why a dropped gate makes a key hard to turn (simplified, not to scale). The lock itself may be fine: the bolt is being squeezed against the edge of the keeper, so the key has to fight that pressure.

When the gate is the culprit, you'll often notice other clues: you have to lift or push the gate before the key turns, the bolt has rubbed a shiny mark on one side of the keeper, or a hinged gate scrapes the ground. Lifting or pushing gently to take the pressure off can get you through today, but it isn't a fix. The gate or keeper needs adjusting before the lock wears out from the strain.

Symptoms and likely causes

Security gate lock symptoms and what they usually point to
Symptom	Likely cause	What you can safely do
Key turns with the gate open but not when it's closed	Gate dropped or out of line; retractable gate not fully closed	Make sure the gate is fully closed; take the weight off gently; book an adjustment
Key goes in but is stiff or gritty in every position	Dirt or corrosion in the lock	Check the maker's care guidance; don't force it
Key won't go all the way in	Wrong or bent key, debris in the keyway, or a damaged cylinder	Check it's the right key and look along it for bends; try the spare if you have one
Key turns round and round, nothing happens	A broken part inside the lock	Stop and call; the lock needs repair or replacement
Slam-lock gate won't catch, or won't release	Latch dirty, worn or out of line with the keeper	Check nothing is blocking the keeper; call if it persists
Key snapped in the lock	A worn key forced in a stiff lock	Leave the broken piece alone and call for broken-key extraction
Lock damaged, bolt bent or keeper ripped after a break-in	Attack on the gate	Report it, leave things as they are and see securing your home after a burglary

Cleaning and lubricating: follow the gate's maker

It's tempting to grab whatever spray is in the garage. Don't, at least not until you've checked what the maker of your gate says, because their advice differs and the wrong product can do harm.

Trellidor tells owners of its gates not to spray into the keyhole of the cylinder where the key fits. Its care guide says to clean the gate with a diluted, salt-free car wash and a soft cotton cloth, to avoid abrasive, detergent-based or solvent-based cleaners, and to apply its lubricating spray to moving parts such as hinge points and top tracks, wiping off the excess.
Some window and door makers take a different line for their own lock barrels. Stegbar, an aluminium window and door maker, recommends powdered graphite in the keyway.

The point isn't which is right in general. It's that each maker knows what's inside its own lock. Oily sprays can collect the dust gates are exposed to and turn it into paste, and a product that suits one mechanism can gum up another. If you don't know who made the gate or lock, leave the keyway alone and ask a locksmith to look at it.

Warranty: Trellidor notes that neglecting maintenance can void a manufacturer's warranty. If your gate is still under one, read its care terms, and check with the installer before anyone else works on the lock.

What makes it worse

Forcing the key, or turning it with pliers. Gate keys snap, and a stub stuck in the keyway leaves the gate unusable.
Hammering the lock or the bolt. It can crack the lock case or bend the bolt.
Spraying penetrating oil or household lubricant into the keyhole against the maker's advice.
Cutting or grinding to get the gate open. You'll be left with a damaged gate and an open door until it's repaired.
Living with it. A gate you have to lift every time gets worse, and the extra strain wears out the lock.

Slam lock or deadlock? Choosing the replacement

If the lock does need replacing, it's worth thinking about the type, not just swapping like for like.

Slam locks lock as the gate shuts, with no key needed. Trellidor lists the downsides: it's easy to lock yourself out, children can lock themselves in or out, and the maker describes them as traditionally weaker than deadlocks. Its own slam lock uses one key in one keyhole, but some gates end up with two separate locks and two keys.
Deadlocks need the key to lock. Trellidor fits a deadlock as standard on several of its retractable gates and says it locks in two or three places along the lock stile.
Five-lever gate locks are common on hinged gates. ASSA ABLOY says the UNION five-lever gate lock is SABS approved, has internal roller pins and an anti-saw feature on the deadbolt, and can be retrofitted to existing gates as well as new ones.

The right choice depends on the gate, who uses it and how. Our guide to deadlocks, nightlatches and mortice locks explains the terms, and lock replacement covers fitting a new lock.

When to call, and what helps

Call when the open-gate test points to the lock, when the key won't turn at all, when a key has broken, or when you're locked out by the gate. We're a mobile locksmith in Roodepoort, so we come to the gate, 24/7. A lock repair or adjustment is tried before replacement where the lock is sound. The call-out fee is R250, the technician quotes on site before any work starts, and payment is by EFT, cash or card.

Photos of the lock from both sides, and of the keeper on the wall or frame.
The result of the open-gate test, if you could do it.
The type of gate: hinged, retractable or sliding, and any brand name on it.
Whether it's a slam lock or a key-to-lock deadlock.
Whether you're locked out or the gate is stuck open and the house can't be secured.
Access details for your complex or estate.

Questions

Can I just use any lock spray from the hardware store?

Check the gate maker's guidance first. Trellidor, for example, says not to spray into the keyhole of its cylinders. If you don't know the maker, leave the keyway alone and have it looked at.

My security gate is stuck open and won't lock. Is that urgent?

If it leaves the house unsecured overnight, yes. Tell us that when you call. Make sure the front door behind it is locked in the meantime.

Do I have to replace the whole gate if the lock fails?

Usually not. Most gate locks can be repaired or replaced on their own. A gate that has dropped or is damaged may need adjusting or repair as well.

Need a locksmith to look at it?

If this hasn't solved the problem, our lock repairs service covers it. We're a mobile locksmith in Roodepoort, so we come to your door.

Sources and further reading

Trellidor: Dos and don'ts of retractable security gates — Don't spray into the keyhole of the cylinder; clean with diluted salt-free car wash and a soft cloth; no abrasive, detergent- or solvent-based cleaners; lubricate moving parts, hinge points and top tracks; wipe off excess
Trellidor: Why do security barriers need maintenance? — Gates sticking when closed is an early sign of neglect; neglect can void manufacturer warranties
Trellidor: The myth about slam locks — Slam lock drawbacks; deadlock standard on T700, T800 and T900 retractables, locking in two or three places in the lock stile
ASSA ABLOY: UNION launches its new and improved 5-lever gate lock — Internal roller pins, anti-saw deadbolt feature, suitable for retrofitting, SABS approved, made locally
Stegbar: Maintaining aluminium windows and doors — Recommends powdered graphite in lock keyways for its products, showing makers' advice differs