Verse Keeper Book Darts - Line Marker Bookmarks (Tin of 125 Mixed Metals) Verse Keepers are precision-cut, paper-thin metal line markers that attach easily to any page To use, place Book Dart at desired line, close book and press in.Sliding a Dart onto a passage assures you can recall it easily even in a closed book. Book Darts slide easily on and off the page without damaging your books. Use again and again for a lifetime. Elegant enough for great museum shops, book-friendly enough for public libraries, often judged indispensible by students, educators, and other readers of what has lasting value. Answers the question: