Canadian football, the snap is required to go between the centre's legs; no such move is required in American football, but it is invariably done this way anyway, so the center is in position to block following the snap. The defensive team must stay a set distance away from the line of scrimmage on their side of the line. In Canadian football, the distance between the line of scrimmage and the defensive team, formally called the "scrimmage zone", is one full yard. Because of this one-yard distance, teams tend to gamble on "third and one" or "third and inches". If a team's offense is within one yard of either goal line, the line of scrimmage is moved to the one-yard line. In American football, the set distance between the offensive and defensive teams, known in that code as the "neutral zone", is 11 inches – the length of the ball, creating the illusion of the teams being "nose-to-nose" against each other. While large, relatively immobile offensive line players used to form a line that cannot be easily penetrated by the defense are valued in American football, the extra distance from the defensive team means Canadian football finds value in more nimble players on the offensive line. Fair catches and punt returns In American football, if a punt returner sees that, in his judgment, he will be unable to advance the ball after catching it, he may signal for a fair catch by waving his hand in the air, and forgo the attempt to advance. If he makes this signal, the opposing team must allow him to attempt to catch the ball cleanly; if he is interfered with, the team covering the kick will be penalized 15 yards. In contrast, Canadian football has no such rule; instead, no player from the kicking team, except the kicker or any player who was behind him when he kicked the ball, may approach within five yards of the ball until it has been touched by an opponent. If they do, a "no yards" penalty is called against the kicking team. Penalties for "no yards" calls vary on whether the ball made contact with the ground or not. The penalty is 5 yards if the ball has bounced and 15 if the ball is caught in the air. Furthermore, in American football, the receiving team may elect not to play the ball if the prospects