The last, and arguably most vital innovation, which might finally make American football uniquely "American", was the legalization of interference, or blocking, a tactic which was really illegal beneath the rugby-style principles. Interference continues to be strictly illegal in equally rugby codes. The prohibition of interference in the rugby recreation stems from the sport's strict enforcement of its offside rule, which prohibited any player to the team with possession on the ball to loiter concerning the ball and also the target. At first, American players would uncover Resourceful ways of aiding the runner by pretending to accidentally knock into defenders seeking to deal with the runner.

The field decide is positioned 20 yards downfield from the line choose. source The field decide displays and controls the Perform clock, counts the quantity of defensive gamers on the sector, and watches for offensive go interference and unlawful use-of-fingers violations by offensive gamers.