This object is little more than a wooden plank. It is seen in TDP/TG and T2, and is used as a destructible, albeit noisy, barrier. In DromEd, this is classified as a door, probably because it is made to fit a typical doorway.
In the TG mission "Thieves' Guild", many of the doors in the sewer are boarded up with solid blocks, coloured like planks, rather than the prefabricated object. It is unclear why this was done, as the blocks are less realistic in appearance.