Book Darts Line Markers 125 Count Tin Bronze by Book Dart. Book Darts are precision-cut, paper-thin metal line markers that attach easily to any page. The markers attached easily, simply place Book Dart at desired line, close book and press in. Sliding a Dart onto a passage assures you can recall it as it creates line markers/traces even for a closed book.It slides easily on and off the page without damaging your books. Use again and again for a lifetime. And eliminates: Bent corners, Paper clips, Underlining, Highlighting, "Sticky Papers" (and sticky pages).