To close your book you will need:
A brad and matching eyelet.
A childs hair band, with the metal joiner as it works to hold the elastic in place.
Close your book and mark where the elastic stretches too on the front cover and punch a hole.
Now take your brad and add the eyelet upside down so it creates a post like above, the top of the eyelet is next to the book cover.
Close the brad as tight as you can as normal on the inside front cover of the book,
This now gives you a peg on the front of the book and when you close the book you can wrap the elastic round to hold the book closed.