Mistero at the foot of a door

We just moved into our new condo and observed that another condo on our floor had a “thing” along the foot of their door: (image at right below). which isn’t prresent at the foot of our door (left image). You can see this by comparing the size of the silver metal plates at the foot of the two doors: Note that the silver metal plate at the foot of our door appears to be wider, because the plate at the foot of the other condo’s door is partially covered by the “thing”, which seemed to be like a roll of fabric.

So this mistero has two parts. First, what is the purpose of the “thing”?

You may know, or guess, that cloth rolls like this “thing” are often used in households to cover a gap at the foot of the door so as to prevent cold drafts from entering the room……but these draft-blocking rolls are placed at the foot of the door on the inside, not the outside, of a room!

So this is the real mystery…..How could a person place such a draft blocker on the outside of the door without disturbing it when they went back inside?

What goes on here?