The most common reason a lock doesn't lock is due to misalignment between the door latch and the strike plate.
Here's a breakdown:
Latch Misalignment
According to the provided information, a primary culprit for a door not locking is often the door latch not aligning with the hole in the strike plate.
- What is a Latch?: The latch is the part of the door that extends from the door's edge and fits into the strike plate on the door frame to hold the door closed.
- What is a Strike Plate?: The strike plate is the metal plate that's mortised into the door frame where the latch bolt engages.
Why Misalignment Occurs
Misalignment can stem from several factors:
- House Settling: Over time, houses settle, which can shift door frames.
- Loose Hinges: Loose hinges can cause the door to sag slightly.
- Warped Door or Frame: Changes in humidity can warp doors and frames.
- Improper Installation: The initial installation may not have been perfectly aligned.
Troubleshooting Latch Misalignment
Here's how to see if the latch is the problem:
- Inspect the Alignment: Open the door and visually inspect whether the latch lines up with the hole in the strike plate.
- Test the Latch: With the door open, extend the latch bolt. Does it move smoothly? If it feels sticky or doesn't extend fully, the latch mechanism itself might be faulty.
- Examine the Strike Plate: Look for signs of wear and tear, damage, or improper installation. Is it securely attached to the door frame?
Solutions
While attempting to fix the misalignment yourself is possible, it's emphasized that it's best to call a professional locksmith for repairs. However, here are some potential solutions:
- Adjust the Strike Plate: Loosen the strike plate screws and shift the plate slightly to align with the latch. Then, tighten the screws. You might need to file the strike plate hole a bit larger if the latch is only slightly off.
- Shim the Hinges: Place thin cardboard shims behind the hinges to realign the door.
- Tighten Loose Hinges: Tighten any loose hinge screws.
