This proverb refers to the typical ancient wooden door being attached to a vertical wooden post which turned in upper and lower socketstones (“hinges”) — one on the floor and the other in the ceiling. Like in our homes today, ancient doors opened and closed on hinges along only one side of the doorway.
Some translate “hinges” as “pivots,” because it comes from the Hebrew verb “to turn.” So the lazy guy (“sluggard”) keeps turning back and forth in his bed, like the doorpost keeps turning open and closed in the socketstones.
This isn’t a new insight, just an analogy that lazy men stay in bed, turning over again and again. All a door does is turn back and forth and this guy can’t be counted to do any more than just that!
Want to see a little more about ancient doorways on site in the Holy Land? Visit: http://www.youtube.com/watch?feature=player_detailpage&v=Vg8pIOvvLxw.