A bookmark is a thin marking tool, commonly made of card, leather, or fabric, used to keep track of a reader's progress in a book and allow the reader to easily return to where the previous reading session ended. Alternate materials for bookmarks are paper, metals like silver and brass, silk, wood, cord (sewing), and plastic. Some books may have one or more bookmarks made of woven ribbon sewn into the binding. Furthermore, other bookmarks incorporate a page-flap that enables them to be clipped on a page.