 FACT: In the film, the emperor and crowd put their thumbs up for  live and down for kill. However, in reality the emperor would  use his four fingers to cover his thumb as the sign to let the  gladiator live. When he wanted the gladiator to die he would put his  thumb straight out to the side symbolizing the sword. The gladiator  could also be let to live if the emperor threw a piece of cloth or  something of the sort showing mercy or yelling the Latin word for  "dismissed". Study of ancient artwork suggests that the "thumbs up"  gesture was actually an affirmation to proceed with the kill.