Check this out!
Why he chose a nut and bolt, we'll never know.
But I do know that folding the paper to look like the threads on a bolt is really impressive! I think the origami world was super impressed too because lots of people have recreated it - just do a Google Image search of "David Brill Origami Nut Bolt" and you'll see plenty of examples of people recreating them.
You could also:
It looks too hard and time consuming for me...I'm busy blogging!