Before installing a Lockking Sliding Glass Door Lock you should raise your sliding glass door up and still slides easily. This will keep someone on the outside from pushing up on the sliding door and unlatching most factory latches.
To do this you will need the right kind of screwdriver, either a philips or slot driver. By looking into the hole at the bottom edge of the sliding door you can determine which screw driver will work. There is a roller adjustment screw on both sides of the sliding door. By inserting the screwdriver into the adjustment screw in the door you can raise or lower the door.
Raise one side a little and then the other in order to keep the edge of the sliding door aligned with the side jamb. If it seems to hard to turn the screw you might need a friend to lift that edge of the door to take the weight off of the adjustment roller.