This is a simple but useful project. All you need is big sticky note and scissors. You follow the template in my picture and cut out the line (dashing line is mountain fold, long dash and dot is valley fold). After you follow the template, fold the book mark in half and fold the other at two edges of the thick part. To use, stick the sticky edges in to the cover of your book. When you open the book, it will fold up but when you close your book, it automatically fold down and mark your last read page.
P.S: sorry about my bad English