Our back door has a window in it, two sidelights and a transom. The windows on each side are tall and skinny with a divider separating the two panes, but they are not double hung. They have thick layers of paint over them, so it's possible they might open in some way but none that's obvious.
Then at the bottom of each window is a little knob:
The knob turns freely from the outside, and has a screw-like end that pokes through the middle of the window sash and out the other side. It looks like there might be a corresponding hole on the underside of the window frame above the screw end.
For the life of me, I can't figure out what this thing does/did. The knobs are shaped somewhat like an old-fashioned doorbell twist, but they can't be that. We've had one suggestion that they could've once controlled window blinds. But then why would the knobs be on the outside?
It's weird all around, and I've seen nothing like it in any of our neighbors' houses. I'm hoping someone out there has seen one before or has an educated guess.