Challenge your students to CRACK the call number code with a little help from some QR codes. You select several books from your library's fiction picture book, fiction chapter book, and nonfiction sections. Attach the QR code that identifies what type of book it is. Mix the books together and place in your center. Students sort the books according to their call numbers, then check their work by using their device to scan the books' attached QR codes. Center materials include copies of QR codes to attach to books, center activity/direction card, and book labels for sorting.