hi there in order to do anything you have got to open the door. there are a number of ways the door lock is not operating correctly.Will try and outline these easiest fault first . simple out of adjustment door could be opened by lifting the sash and opening the door at the same time. Adjust catch up or down ( screwed into frame)
More difficult the sliding lock mechanism has came adrift or the bar has snapped you need someone that has experience to open the door. Locking mechanism needs replaced in most cases
bob
