Antique books were made by printing multiple pages on both sides of one large sheet of paper, folding it repeatedly down to single-page size, and trimming the edges. When you received a book it was not uncommon to find some un-trimmed pages. Paper knives had dull blades with which to split the fold in order to open the pages. Folding knives made with ivory handles and blades are sometimes marked “Paper Knife” but can also be marked “Fruit Knife.”