The third prong on an electrical cord is the ground plug. Since plenty of cords have only two, it may not seem terribly important—but according to national electric code, it's an important safety feature that could save your life. Literally.

Washington, D.C. -- The U.S. Consumer Product Safety Commission (CPSC) is warning consumers to immediately stop using and discard male-to-male extension cords sold on Amazon.com due to shock, electrocution, fire, and carbon monoxide poisoning hazards.