A gun is a different matter. While a clock is set to run for a specified time period, a gun can be pulled out at any moment to bring the story to a climax. It’s called a gun because of Chekhov’s directive that if a character puts a gun in a drawer in act 1 he or she must pull it out in the final act. A classic example is the faulty furnace in The Shining. We’re told early on that it will explode. The story might stagger on until springtime, but for the fact that…the furnace explodes.
