A sliding glass door that will not lock has usually dropped. Worn rollers let the panel sit low, so the hook on the mortise lock no longer meets the keeper on the jamb. Other causes are a worn-out mortise lock, a keeper that has shifted, a bent hook, or a handle that spins free. New rollers and an adjustment, or a new mortise lock, fix it in one visit.
Likely causes
- The panel has dropped on worn rollers, so the lock hook misses the keeper
- A worn mortise lock: the hook does not throw, or throws and will not hold
- A keeper that has shifted or loosened on the jamb
- A bent or broken hook, often from forcing the handle
- A handle that spins without turning the lock: stripped spindle or broken lock body
What you are seeing
You pull the door closed, lift the handle or turn the thumb-turn, and nothing holds. The hook comes out but lands below or beside the keeper. Or the handle moves and the hook never appears at all. Or the hook catches but a tug on the handle pops it open.
Often the door also sits a little low on the lock side, and you have been lifting it as you close it to make the lock catch. That trick works until it does not.
A door that will not lock is the one slider problem people do not put off, and it is usually a quick fix.
What usually causes it
A dropped panel. The handle set carries a mortise lock whose hook swings up into a keeper on the jamb. When the rollers wear, the panel drops and the hook arrives below the keeper. This is the cause on most doors we see, and the clue is that the door is also harder to slide than it was.
A worn mortise lock. The spring or the cam inside gives up, so the hook sags, will not throw fully, or will not stay thrown.
A moved keeper. Screws loosen, the keeper slides, and the hook misses.
A bent hook or spinning handle. Forcing a misaligned lock bends the hook or strips the spindle that connects the handle to the lock, so the handle turns and nothing happens.
Need your sliding door locking again this week?
Call or text with your address, how many doors and what the door is doing. You get a firm price before we come out.
What you can check yourself in two minutes
- Watch the hook. With the door open, operate the handle and watch the hook come out of the edge of the panel. If it does not move, the problem is the lock or the spindle. If it does, close the door slowly and watch where it meets the keeper.
- Check the gap at the top. If the top gap is wider at the lock side, the panel has dropped. That points to rollers.
- Look at the keeper screws. Loose or missing screws mean the keeper has moved; tightening them may be all it needs.
- Try a quarter turn. Turn the roller adjustment screw at the bottom lock-side corner a quarter turn to raise that corner and test the lock. If it locks and stays locked, an adjustment may be enough. If nothing changes, the rollers are done.
Do not force the handle. A bent hook turns a cheap fix into a lock replacement.
What we do about it
We fix the cause, not the symptom. If the panel has dropped, we fit new tandem rollers and set the height so the hook meets the keeper square. That is the repair on most doors that will not lock, and it is why our lock calls often end as roller jobs.
If the mortise lock is worn, we replace it. Mortise locks come in a handful of common sizes and hook styles, and we carry the ones that fit most patio doors, including keyed and non-keyed sets. If the keeper is damaged, we fit a new one. If the hook is bent, the lock is replaced; a bent hook does not hold reliably once straightened.
See lock and handle replacement and roller replacement.
When it is not worth repairing
A lock that will not catch is almost never a reason to replace a door. The two exceptions:
- The jamb the keeper mounts to is rotted, cracked or so chewed by old screw holes that nothing will hold. That is sometimes a frame repair rather than a door replacement.
- A very old or unusual lock body with no matching replacement, where the handle hole pattern in the panel does not suit any current set. We can usually still make something fit, and we tell you before we start if we cannot.
If you want more than the factory hook, we add a secondary lock: a foot bolt, a pin lock or a keyed auxiliary lock. Our sliding door lock security guide covers the options and their limits.
Across San Diego
Doors that will not lock are a tenant-turnover and a vacation-rental problem as much as a homeowner one. In Pacific Beach and Oceanside rentals the slider is the door guests use most, and a lock that catches only with a lift is the first thing a property manager hears about. See vacation rentals and HOAs.
On the original aluminum doors in Chula Vista and El Cajon the lock is often a keyed mortise from the 1970s that has simply worn out; old aluminum doors take current replacement locks more often than people expect. Vinyl Milgard and Pella doors usually just need rollers and an adjustment to lock again.
Will Not Lock or Latch: common questions
Why won't my sliding glass door lock anymore?
Most often the panel has dropped on worn rollers, so the hook on the mortise lock arrives below the keeper and cannot catch. The fix is new rollers and a height adjustment, not a new lock. If the handle moves and the hook never appears, the mortise lock or its spindle is worn and the lock is replaced.
Can you fix a sliding door lock without replacing the whole handle?
Usually. The mortise lock is a separate part that slides into the edge of the panel behind the handle, and on most doors it can be replaced on its own. If the handle is cracked or the spindle is stripped, we replace the handle set, which includes a new lock.
How can I make my sliding glass door more secure?
Start with a lock that actually catches: fix the rollers so the hook meets the keeper. Then add a secondary lock, such as a foot bolt, a pin lock through the frames, or a keyed auxiliary lock, and make sure the anti-lift block in the head channel is in place so the panel cannot be lifted out.
Do you replace keyed sliding door locks?
Yes. We carry keyed and non-keyed handle sets with mortise locks that fit most patio doors, and keyed auxiliary locks for doors that never had a key. The price is agreed before the visit.
Is a sliding door that will not lock the landlord or the tenant to fix?
In a rental, a working lock on an exterior door is normally the landlord or property manager to fix, not the tenant. Report it in writing with a photo of the hook missing the keeper. Property managers can book us directly; see our landlords and property managers page.
More answers on the FAQ page. Not sure what your door has? Send us a photo and we will tell you.
Where we see this
We cover all of San Diego County, usually within the week. Some of the places we work:
Related guides
- Sliding Glass Door Locks and Security in San Diego: What Works – Why a dropped door will not lock, mortise lock and keeper replacement, keyed vs non-keyed handles, secondary locks that work, and what renters can do.
- Signs Your Sliding Door Needs New Rollers (And Two-Minute Checks) – Symptoms of worn sliding door rollers in order of certainty, the two-minute checks you can do safely, and how to tell when the track is the real problem.
- Sliding Door Off the Track: What to Do Right Now – Safe steps when a sliding glass door panel has jumped its track: what to do first, what never to do, why it came off, and what the repair involves.
Ready to get the door gliding again?
Call or text for a straight answer and a price before we come out. Mon to Sat 7am to 6pm.