This accordion-fold Sketchbook, known as Cè Yè (册页）, is a traditional form of book binding in ancient China used for mounting calligraphy and painting works. It originated from scroll binding and evolved into thread-bound books. This Che Ye  sketchbook format emerged during the Song Dynasty, influenced by book sketchbook packaging. It is highly valued by calligraphers, painters, and collectors due to its small size, ease of creation, and preservation. Typically, hard shell boards covered in Song brocade serve as the front and back covers, creating a book shape when folded.