 Prominent use of the figure "X". Its first appearance is under the  opening credits and from then on, whenever a character dies, the  figure "X" is prominent in the scene. Some examples: during the  shooting in the bowling alley, a pencil fills in a strike box on a  scorecard. When a recreation of the St. Valentines Massacre is  shown, the scene begins in the rafters of the garage, where the roof  support beams are seven "X" shaped pieces. When Tony kills his best  friend at the door of his apartment, the number on the door is "X".  This was done for a reason: newspapers at the time printed photos of  crime scenes. The "X" would be used to mark the spot of where the  body was found.