Why A Zener diode uses the standard diode outline, a triangle pointing at a bar, but the cathode bar has short flags bent off each end so it looks like a letter Z or a flattened S. That bent bar is the only visual clue that distinguishes it from an ordinary rectifier diode, and it signals a device meant to conduct in reverse at a fixed breakdown voltage for regulation. In figure G7-1 that triangle-with-bent-bar is the fifth symbol.