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Patio doors lead to the outside and have to withstand all kinds of abuse from the weather, doors being slammed and being hit with flying objects. As a result, your patio door lock can malfunction. If your patio door isn't locking, repair it quickly so that your home remains safe. Locks keep out people you haven't invited into your home and give you peace of mind when you go to bed at night. You can solve many patio door problems with a few simple tools and tips.
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Check the plate where the lock catches in the door frame. Be sure there is no buildup or object keeping the lock from latching. Use your finger to clear away any debris. Use a screwdriver to make sure all the bolts on the door frame plate are tight.
Open the patio door very slightly, and turn the lock. If it comes out, watch to see whether it connects with the lock catch in the door frame. It it doesn't, check to be sure the door is properly aligned. You might need to prop the door up and tighten its connection to the door frame.
Open the door completely, and twist the lock as usual. Watch to make sure the lock extends from the door where the knob is positioned.
Smear petroleum jelly on the lock itself, and close the door gently. Attempt to turn the lock. Open the door and check to see where the petroleum jelly has transferred to the latch on the door frame. If it isn't in alignment with the lock, that might be why the lock is not working. Determine how far out of alignment the lock is, and reinstall the latch plate in the door jamb by unscrewing it, sanding the wood and replacing it so it meets up with the lock perfectly.
Remove the doorknob from the door, and clean the latching mechanism. Oil it once it is clean to ensure it slides smoothly in and out of the lock. If the lock itself still won't slide out, you might have to replace the entire locking mechanism inside the door knob.