Sliding glass doors are typically only lockable from the inside; they are not used as entry doors. However, you may decide to use your sliding glass door as a regular entry point, in which case you might want to think about installing a key lock so the door can be unlocked from the outside. A key lock can also be installed on the inside of the door for added security against intruders or to keep small children from opening the door.
Clean the door frame with hot, soapy water and allow it to dry completely.
Place your head near the frame and tap it with the end of a screwdriver until you hear the sound change. This indicates there is no glass behind the frame. Mark the spot on the frame. Hold the new lock up to the door to determine where the lock and screw holes should be drilled. Mark each screw hole.
Place the metal punch over the marked spot on the frame. Tap it with a hammer gently to create a hole. Drill the hole out until the lock fits inside. Drill out any holes necessary for the lock-securing screws in the same way. Secure the lock with mounting screws.
Mark the door frame for the latch plate. Drill any necessary holes and secure the latch plate to the frame. Test the lock.