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.
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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.