Sensu: Nine and Five
In my research, I have found numerous examples of utensils that manifest or suggest 9 and 5 together. For example, the length of the kazari hi-bashi, 飾火箸, is 9.5 sun kane-jaku. The length of the sensu, 扇子, fan-of, pictured above is 10 sun kujira-jaku. The length of the sensu sen-men, 扇面, fan-face, paper is 5.7 sun kujira, the length of the exposed part of the ribs is 4.2 sun kujira. When the both lengths are compared, the ratio is 8 to 10. The number 18, jū-hachi, 十八, ten-eight, is symbolic of Infinity in Space and Time, and when 18 is divided in half it equals 9.
This standard large sensu has 5 ribs that support 9 paper panels of the senmen. The sensu has the shape of the number hachi, 八, which is a manifestation of sue-hiro, 末広, ends-wide. As it is a folding fan, there are 8 folds of the senmen. Again a representation of Infinity in Space.
The numbers kyū, 9, and go, 5, may by read kyūgo, which is a homonym for kyū-go, 救護, salvation-protect, which is an attribute of Kannon Bosatsu, Jizō Bosatsu, and other deities.
For further study see also: Chashaku and Sensu