傳世的晉唐法書名蹟（包含可靠的雙鉤模本）數量不多，然出現節筆的作品不少，已成為晉唐法書的重要特徵。此現象在書法史界已有相當的研究成果，確認摺紙即為造成節筆的主因。然而，當摺紙現象被充分描述與說明之時，摺紙的功能卻懸而未解，多數論者僅單純視之為書寫定位，然此說並無法解釋傳世書蹟中的種種節筆現象。事實上，北宋以前桌椅尚未應用於書寫，持紙仍是主要的書寫方式，為便利持書的操作，直接於紙面上施以摺痕，加強紙張的支撐力，又因為稿本的性質，便造成節筆的出現。由晉唐時期的實際書寫脈絡來理解摺紙，不僅對這些珍貴的早期書蹟有更深的認識，也能釐清長久以來無法解釋的節筆現象。

Bamboo joint strokes are regularly found on the handful of extant calligraphic works of the Jin and Tang dynasties, and are considered one of the distinguishing features of these works. These special strokes have been the subject of considerable scholarship. Most research attributes them to creases in the paper and regards them as little more than registration marks for positioning characters. However, this ”positioning” hypothesis fails to explain many examples of these strokes in Jin and Tang calligraphy. It is therefore necessary to reconsider the causes of these folding marks in the context of writing method and writing environment. Before the Northern Song dynasty, the most common way to write calligraphy was by holding the paper in the hand rather than laying it flat on a desk or table. In order to create a steady surface for writing, the paper was often folded to strengthen its structure. The likelihood that many extant pieces were drafts rather than final works further explains the presence of unintentional bamboo joint strokes. In sum, considering creases in the context of actual Jin and Tang writing practice offers deeper insight into the early history of Chinese calligraphy by explaining the mysterious phenomena of the bamboo joint stroke.