Thats why the teeth line the bottom of it in case anyone happens to be below, like the unfortunate rancor.
Huh... I always thought the teeth on the bottom of the door were meant to add an extra layer of protection, to keep the door from buckling if a heavy creature like the Rancor was ramming it, trying to get out. I figured there were corresponding holes in the floor that were reinforced to eliminate any weak spots.