People have been speculating about this since the Inaugural Parade (above); but I've seen at least one video of him opening a door for her using his so-called fake hands. Notice in the pic above the fingers change positions on both hands. It appears that it's just a habit he has. His entire build is a bit unusual.
I do see that in all the photos of him on this post, his coats are cut very wide around the midsection, which is where the holster(s) may be strapped.
