In a bookstore, "real estate" is everything. Books are often shelved "spine-out," meaning you only see the thin edge. However, when a bookstore displays a book "face-out," the shelf note becomes the primary tool for grabbing your attention without cluttering the cover art.
Injuries such as Erb-Duchenne palsy (C5-C6 roots) resulting in a "waiter’s tip" position, or Carpal Tunnel Syndrome involving the median nerve. shelf notes anatomy