It looks daunting if not downright dangerous – two side supports, anchored to nothing and angled away from normal (in the sense of: ninety degrees from the ground) look little like legs, and the seat swings freely between them.
Still, this is basic physics at its best – adding the gravitational pull of the Earth as well as human weight makes it more stable, not less. While it would not work in space or some other zero-or-anti-gravity situation, it would be a wonderful seat to lean against your home on your deck or porch.
Designed by Bernhard Burkard, the connections and materials are quite basic – metal fasteners hold together a wood frame, which in turn supports a canvas lounge chair. Rubber stoppers add frictional resistance to hold the whole thing in place.