I saw an old textbook on Kikujutsu, about a Japanese carpenter's technique. It's printed on Japanese paper... (Washi,precious!) It's written in Kanji or broken Hiragana, well, I can't read it. . . However, the L-shaped ruler called Sashigane in the figure is still used by current carpenters, and they sometimes mark it like this. Using this one tool, they quickly mark the material with the dimensions determined by trigonometric functions (sine, cosine, tangent, etc.). .
The second one is a miniature Sashigane that I had at home. The carpenter's scale has Syaku-sun scales on the back (front or front), but the miniature is only centimeters. Instead (?) it's named Sunsun-boshi. (Issun-boshi is about 3 centimeters tall.) Twenty years ago, when I first designed a wooden structure house, I was surprised by the carpenter's calculations. Actually,they calculate by Syaku-sun scale. I've grown up with centimeters and millimeters (metric), so I'm still not used to Syaku-sun scale, but in reality, things that take time to make are more suitable for our head and body.
