"I don't know if that's his invention. It looks a lot like the Chopstick Jig from Kakuri. I saw it at the timber show in the middle of last year in Melbourne and my woodworking teacher has had one for some time before that (she finds it useful for making timber pegs). It's available from this Australian stockist: https://www.japanesetools.com.au/products/chopstick-maker-jig"