Thanks landlord for not messing around when it came to my back door. There’s a convenient latch which by itself would not have been enough since someone could break the glass and turn it. So you also included a key-operated deadbolt and an additional giant lock up top for good measure. I’m all set for holding off zombies … but why the chain? What’s your logic there? What’s the point of a chain lock on a door you can see out of anyway and where no one would ever get a delivery?