What is satsudou?

As an AI language model, I do not have enough information about the term "satsudou." It is possible that you meant "Satsu-dou," which refers to the Japanese art of bookbinding. Satsu-dou is a traditional method used to bind books, utilizing folded sheets of paper or vellum sewn together, and then glued onto a cover. The technique has been used for hundreds of years and is still used today in Japan and other countries. The binding creates a book that is sturdy, but with a soft flexibility that allows it to lay flat when opened. It is a time-intensive process that requires a great deal of skill and patience to master.