The Death Star's Exhaust Port

Waiting at the end of a long trench in the Death Star's upper hemisphere lies a critical thermal exhaust port only two meters wide. This single chink in the Death Star's armor is the only hope for the Rebel forces to defeat the sinister Imperial battle station before it uses its planet-destroying laser to obliterate the Rebel Base on the Fourth Moon of Yavin. Thoroughly ray-shielded against laser fire, the port can only be hit with proton torpedoes, making split-second timing of the torpedo fire absolutely critical.

During the Rebel attack against the Death Star, the Rebel X-wing pilot Red Leader fires his torpedoes at the exhaust port but scores only a near miss, one of the torpedoes striking the side of the trench (causing substantial damage) and the other leaving an impact scar close to the exhaust port. Even the X-wing targeting computer was not able to hit the port, leaving the hope of the Rebellion with Luke Skywalker, who turns off his computer at the last second.