A sign on the window to the tiny balcony at our hotel in Kansas City:
Perhaps I’m a little unclear on the concept of door, but it seems to me that a door in use is closed since the function of a door is to partition space with a variable setting of partitioning space or allowing passage. To me, the “on” setting actively partitions the space, whereas the inactive or “off” setting, that is the setting that would exist if the door was not even there, allows passage.
Ergo, I would not think you could lock a door when it is not in use, since a door not in use is open.
Of course, it is possible I overthink things.