Shinobu Kobayashi is a Japanese woodworker based in Australia, currently studying Scandinavian techniques in Sweden. The three-continent background appears to have done him well; working in concert with a master cabinetmaker from Denmark, Kobayashi managed to cut this crazy three-way woodworking joint:
According to Kobayashi, this "not popular Japanese joint" is called kawai tsugite and was invented by a Japanese professor at Tokyo University.
I couldn't figure out how the darn thing works–but Matthias Wandel, who didn't even know what the joint was called, managed to figure it out only by watching the video above! Here he explains it, and reconstructs it:
It's not surprising what happens at the end, but I think the joint is intended to be a mental/crafting exercise more than a practical technique.
Friction welding is a process whereby two pieces of like material, typically plastic or metal, are rubbed together at high speeds. The resultant heat essentially melts the adjoining surfaces together. ...