Open the sliding glass door.
Remove the screws from both sides of the handle and pull out the handle cover.
Measure the screw points for the handle, the height and the width using a ruler to determine the size of your replacement handle and locks. Buy a handle from the door manufacturer to match the style and handle size.
Place both sides of the new handle in place and insert the screws. Tighten the screws with a screwdriver and test the lock with the new key. Move the handle up or down if the lock is not catching properly.