Hida tools says: “The knowledge of squares evolved to a special skill called “kiku-jutsu,” and its complexity makes it one of the hardest, but most important, skills used in Japanese architecture. In Japan there is even an old saying expressing the sorrow of a carpenter struggling to master a square-“Like a sparrow crying on the corner of the eaves, so does the carpenter cry over the corners”. Is this - スズメが軒の隅で泣くように、大工も軒の隅で泣くのです。