Endpapers, also known as endsheets, are folded sheets used in bookbinding. If they are not included as self-ends in the content pages, they are added separately. One half of the endpaper is glued onto the inside cover, while the other half serves as the first or last free page. Endpapers are typically made from thicker paper, similar to the content pages, and they can be printed, left blank, or made from pre-colored paper for added customization.