[kaisen]

I've seen wheeled upper stops like that where the door would come in contact with something in its swing (like a canopy or awning). I'm going to guess that in this case it would be used as a door-prop for housekeeping (spring loaded door closure?) where that wheel fits juuuuust under the doorframe of the closet and keeps it from closing. But it will pop back under that frame with a tug to close it when you want it closed.