Direct answer: A window that won’t latch is usually not a broken lock first. Most of the time the sash is sitting slightly out of position from dirt in the track, paint buildup, a swollen frame, or a window keeper that no longer lines up with the latch.
Most likely: Start by checking whether the sash is fully seated and square in the frame, then look for debris, paint, or a visible mismatch between the window latch and window keeper.
Separate the problem early: some windows won’t latch because the lock is fine but the sash is riding high, cocked, or blocked. Others close tight but the latch still won’t grab because the window latch or window keeper is bent, loose, or worn. Reality check: a window can be only an eighth inch off and still refuse to lock. Common wrong move: cranking the latch harder until the screws strip or the sash cracks.
Don’t start with: Don’t start by forcing the lock handle or buying new hardware before you know whether the sash is actually reaching the keeper.
The sash looks almost shut, but one corner stays proud of the frame or you feel resistance before the lock lines up.
Start here: Check the track, sill, and meeting rail for dirt, paint, or a sash that is sitting crooked.
The sash sits against the frame, but the latch hook lands above, below, or beside the keeper.
Start here: Look for loose screws, a shifted keeper, or a bent latch at the meeting rail.
The handle moves, but it does not hold the sash tight or it slips out with light pressure.
Start here: Inspect the window latch for wear, stripped mounting holes, or a keeper that is too far away to hold.
You have to shove the sash, lift it, or push one side harder than the other to get close to locking.
Start here: Check for paint bind, swollen wood or vinyl movement, and frame sag before blaming the lock.
This is the most common cause. A little debris in the track or one balance hanging up can leave the meeting rails out of line just enough that the latch cannot reach.
Quick check: Close the window slowly and watch the gap on both sides. If one side touches first or the top rails do not meet evenly, the sash is out of position.
Older painted windows and windows with dirty tracks often stop short before the latch point, even though they look closed from a few feet away.
Quick check: Run a finger along the sill, side tracks, and contact points. Look for paint ridges, packed dirt, or weatherstripping folded into the path.
If the sash closes evenly but the lock misses by a small amount, the keeper is often loose, bent, or mounted slightly off after years of use.
Quick check: Try moving the keeper gently by hand. If it wiggles, sits crooked, or shows shiny wear marks off to one side, alignment is likely the issue.
When the handle moves without grabbing, or the hook no longer pulls the sash tight, the latch itself may be worn out or the mounting screws may no longer hold it square.
Quick check: With the window open, operate the latch and watch the hook or cam. If it barely moves, looks bent, or the base shifts on the sash, the latch is suspect.
You want to know right away whether this is a closure problem or a hardware problem. That keeps you from replacing a good latch on a crooked sash.
Next move: If the sash now closes evenly with gentle pressure and the latch lines up, the problem was likely minor mis-seating or debris and you can move on to cleaning and verification. If the sash still sits crooked, rubs hard, or needs force to reach the frame, keep working the alignment and obstruction checks before touching the lock hardware.
What to conclude: A square, easy-closing sash points toward latch or keeper trouble. A crooked or resistant sash points toward track, paint, weatherstrip, or frame movement.
Packed dirt, insect debris, paint drips, and folded weatherstrip are common, low-risk causes and easy to fix without buying anything.
Next move: If the window now closes fully and latches without force, the issue was blockage rather than failed hardware. If it is cleaner but still stops short or sits unevenly, check for paint bind, swelling, or a shifted sash next.
What to conclude: A window that improves after cleaning usually had a simple physical obstruction. No change means the sash position or hardware alignment still needs attention.
If the window is hard to move and hard to latch, the sash may be rubbing because the opening changed shape or the finish built up over time.
Next move: If a small paint ridge or loose keeper screw was the issue and the window now latches normally, finish with a few test cycles. If the sash still needs lifting or side pressure to latch, the frame or sash alignment is off enough that hardware replacement alone may not solve it.
Once the sash is closing as well as it can, you can tell whether the hardware itself is the reason it still will not lock.
Next move: If tightening or repositioning a slightly shifted keeper restores a solid latch, you likely do not need replacement parts. If the latch still misses, slips, or feels loose after the sash is closing square and the keeper is secure, the hardware is the likely failed component.
At this point you should know whether you have a keeper problem, a latch problem, or a larger fit problem that needs a carpenter or window pro.
A good result: If the window closes evenly and latches with light hand pressure, the repair is done.
If not: If new hardware does not fix it, the root problem is fit and alignment, not the lock pieces.
What to conclude: Successful hardware replacement confirms a worn latch or keeper. No improvement after correct hardware points to sash geometry, frame movement, or a more involved window repair.
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Usually the sash is stopping just short of its true closed position. Dirt in the track, paint buildup, folded weatherstripping, or a sash sitting slightly crooked can keep the latch from reaching the keeper.
No. That often strips the screws, bends the latch, or cracks the sash near the hardware. If it will not catch with normal hand pressure, find out whether the sash is out of line or the keeper is shifted.
If the window closes evenly and the latch still slips or will not grab, the latch is often worn. If the latch lands high, low, or off to one side of the catch, the keeper is often loose, bent, or misaligned.
That points to sash or frame misalignment, not just bad hardware. The latch is only lining up when you manually correct the sash position, so replacing the lock alone may not solve it.
Replace both when both pieces are worn, visibly mismatched, or you cannot get a solid catch with one new piece against one badly worn old piece. If only one part is clearly damaged and the other is sound, replacing the failed piece is usually enough.