representing the last defense against a breakaway play, and the position from which to field opposing kicks. Approximately, on defense, the quarterback and fullback exchanged positions from what they'd been playing on offense, and the quarterback became the safety. Still, when at the beginning of the 20th century, a penalty was introduced for hitting the opposing kicker after a kick, the foul was at first called "running into the fullback", inasmuch as the deepest back usually did the kicking. Confusion increased when the legalization of the forward pass made it more advisable for teams to defend with fewer on the line of scrimmage and more behind. Although the offense could no longer play "guard back", for instance, the defense had no such limitations. A common defensive formation was the 6-2-3 or 6-2-2-1, shown below arrayed against an offense's straight T: S HB HB C FB E_ T__ _G G_ T _ E E T G C G T E QB HB FB HB The so-called center and fullback are playing left and right versions of the same position. The positions were later renamed "linebacker". However, that did not become the usual way to name that position until platoon football became common, with players specializing in offense or defense, substituted according to which team has the ball. There seems to have been some tendency for defensive positions to be named for where the player would play on offense, although quarterback and safety formed an early exception. When linebackers are playing close to or level with the line, a somewhat reliable way to distinguish them from line players is that the defensive line players will be in a three- or four-point stance, meaning that they will be supported by one or both hands, in addition to feet on the ground, while the linebackers will have only feet on the ground. Line players with one or both hands on the ground are called "down linemen"; typically all defensive linemen are so positioned. Alternate position naming schemes for an offensive formation are illustrated below in a version of a single-wing formation: E G C G T T E QB HB HB FB E T C G G T E QB FB WB TB In the top illustration the center is flanked by guards in the 4-2 unbalanced line (four players on one side, the "strong side" of the center, two on the other, "weak",