I went down in my basement and found a couple of what I guess are sleeves. This short piece of EMT goes from one side of a beam in my house to the other, over the beam between the floor above and the beam (a gap of about two inches). I suppose it has a sleeve due to the floor nails protruding out like teeth from the underside of the floor.

http://stevelutzphoto.smugmug.com/photos/490218631_ZxxWF-M.jpg

http://stevelutzphoto.smugmug.com/photos/490218732_zBG9f-M.jpg

Another spot, under the bathroom closet, had a line going up from the basement to the first floor. I suppose this is a sleeve as well. I know some sort of protection is required when going through a floor, so I guess this is it.

http://stevelutzphoto.smugmug.com/photos/490218700_FjWJn-M.jpg