A manuscript fragment may consist of whole or partial leaves, typically made of parchment, conjugate pairs or sometimes gatherings of a parchment book or codex, or parts of single-leaf documents such as notarial acts. They are commonly found in book bindings, especially printed books from the 15th to the 17th centuries, used in a variety of ways such as wrappers or covers for the book, as endpapers, or cut into pieces and used to reinforce the binding.

Source: Fragmentology (manuscripts) – Wikipedia