One of the most common issues with a sliding patio door is that the lock has "play" when the door is locked. A patio door should have no play when you lock or latch the door closed. Fixing a door lock on a patio door is a simple process requiring the use of only one hand tool. Just as there are adjustment screws for the patio door rollers, there is also an adjustment screw for the door lock.
Slide the patio door to the open position. Engage the lock mechanism on the door. There is usually a thumb latch to engage the door lock.
Locate the latch adjustment screw on the edge of the door lock where the latch comes out of the door. There is a screw on the top and bottom of the latch assembly that secures the latch to the door. A screw just above the latch adjusts the depth of the latch.
Turn the screw counterclockwise with the screwdriver to recess the latch into the door. Turn the screw one full turn and disengage the door latch.
Close the door and lock the latch. Pull on the door handle to determine if there is still excessive play. Continue adjusting the latch until there is no play when you pull on the handle with the door in the locked position.