Rule of Thumb :  
  If a cast iron piece is less than 6 inches:   " It is usually a BOOKEND. "

  1. Commonly, Bookends have Sides that are straight and perdicular to the base
    Below is an Example

  2. Some Bookends have a flat protrusion extending
    from the frontside (pictured above) or
    from its backside.(pictured below)
    This is so that the books won't tip the doorstop over


  3. B & H Castings that have NO Protrusions on back
    for Rubber Bumpers are BOOKENDS not a Doorstop

    See example of Edgar Allen Poe's House Below
    Doorstop is on the Left -- Bookend is on the Right