8Column： Function of the curvature

It is not clear when the shaku began to be used, but in China, the legendary first emperor Fushiki has a curved scale on the relief of the Takeshi Shrine stone room in the latter Han Han, so the origin is quite old, and probably came to Japan early in ancient times along with continental architectural techniques. It was truly believed among architects before the early modern times that Prince Shotoku, who was worshiped as an ancestral god, invented the shaku, which was superstition.

By the way, it is said that there are 10 applications for the shaku. It goes without saying that it will become a Ruler when measuring right angles and dimensions and writing lines, but it is a multi-functional tool, such as measuring the gradient, dividing straight lines, and applying the idea of arithmetic for arithmetic purposes, it can also be used as a computer. Of particular note is the function of the backside (square eyes), with a scale of √2 times the front engraved on the back side, and the diagonal side of the right angle triangle is required without calculation. This function is very useful when inking the corner of the building, but Japanese carpenters use the back to solve the complex loading of the roofing material in the corner, and call it "Kiku" techniques. It was highly systematized. However, the learning seemed to be extremely difficult, and the phrase "carpenters and sparrows cry at the eaves" came from here.