There is a line in The Summer Book1 which discusses how bogs, no matter whether you drain them, build over them, or try to change them, simply go on behaving like bogs.
I wonder if it is the same with doors?
Does a door, like the one pictured today—from Pulteneytown in Caithness, Scotland—still believe it is a door, rather than a wall? Or does filling it in change its very nature, turn it into a wall?