"Lu Ban Jing" records that "Lu Banchi is one foot, four inches and four minutes, eight inches between feet, and one inch is one inch and eight minutes." "Bending ruler" is a carpenter's ruler used by ancient carpenters, and its length is the same as the building ruler promulgated by the Ministry of Industry of the imperial court in previous dynasties. Because the building in Ming and Qing Dynasties is 32 cm long, Lu Banchi is 46.08 cm long, and Lu Banchi is 5.76 cm per inch. There are very few Lubanchi handed down from generation to generation. The Palace Museum in Beijing has a Lu Banchi, 46 cm long, which is very close to the length of Lu Banchi recorded in ancient books.
At present, there are two kinds of popular Lu Banchi in China, one is 42.9 cm and the other is 50.4 cm. The length of these two kinds of Lu Banchi is different from that of ancient Lu Banchi.