When it’s aJAR, of course!
Or when it’s a wall, like the door below. This door is in a dance studio in a converted mill building. I guess I’ve been so focused on my favorite instructor (Hi Ali!) that it took me a while to notice it, but as you can see, the door has been permanently closed, and there’s a perpendicular wall that leaves most of the door in the waiting room and the rest in the studio. Add a fancy paint job, a light fixture, and some Great Stuff (insulating foam) and voila! A wall!