The ball begins on the ground with its long axis parallel to the sidelines of the field, its ends marking each teams line of scrimmage in American football; in Canadian football line of scrimmage of the team without the ball is 1 yard past their side of the ball. The snap must be a quick and continuous movement of the ball by one or both hands of the snapper, and the ball must leave the snappers hands. The various rules codes have additional requirements, all of which have the effect of requiring the ball to go backwards to a player behind the line of scrimmage (i.e. in the backfield). The ball may be handed, thrown, or even rolled, and its trajectory and the ball during that passage are called the snap. The snapper is almost always the center. The ball is almost always sent between the snappers legs, but only in Canadian football is that required. Additional rules apply regarding the positioning and stance of the snapper as one of several line players in anticipation of the snap.