The answer to this riddle is spine.
In denoting bravery or courage, 'spine' and 'backbone' are interchangeable. "No spine" is an idiom for the lack of courage and "grow a spine" means to gain confidence and/or courage.
One of Billy Graham quotes says: "Courage is contagious. When a brave man takes a stand, the spines of others are often stiffened."_
In book printing lingo, the spine of a book refers to the outside edge of the book where the pages are gathered and bound.
In addition to providing an anchor point for the pages, the spine provides the hinge action that allows the book’s cover and pages to open and close.
For a huge collection of riddles, puzzles, brain teasers, logic questions, and many more activities to keep you busy for hours, go to www.justriddlesandmore.com.