Folding Stool designed by Jack Smith. Graduate project from the Royal College of Art. Here's a stool by Jack Smith that collapses when its seat is lifted. The stool's three hinged legs fit perfectly into a y-shaped hole in the seat, locking them into place. Via www.dezeen.com
Inspired by Japanese puzzle games, the "Join" table by Ding 3000 links three legs in what's called the "Devil's Knot".