A few reasons! First, the bookmark has the due date and lists any restrictions on use, such as "no renewals." It is a reminder that this book belongs to another library and should be returned to the interlibrary loan office. Also, the transaction number on the bookmark is used by library staff to identify this book in the ILLiad system. Be sure to return the bookmark when you return the book. You may ask the staff member to give you a signed receipt. Receipts are at the bottom of each bookmark.
