footed) snap, the positions of the three scrimmagers were replaced by a single position called "snap". The position names in the winglines were retained for a while, but eventually replaced by the American nomenclature, although it was not until the 1960s, that Canadian rules required seven players on the offensive line, unless they were playing short handed. Before that, only five were required on plays in which no forward pass was thrown, so it is likely that in such situations, one or both ends were replaced by or became a back. "Snap" became "centre" and considered a wingline or line position. "Centre" even became the rule book designation of the snapper, although as in the American version, there is no necessity that the player who snaps the ball have equal numbers of teammates flanking him or her on the line. More position names A tendency was seen, from early on, for players to keep their position names even when playing out of that position. For instance, before the minimum number of players on the offensive line was fixed at seven, when players who would otherwise be in the line as guards or tackles played from offensive backfield positions, the formation was known as a "guard(s) back" or "tackle(s) back" formation. Meanwhile, another position name was introduced. Players were placed in the offensive backfield just outside their ends, in a position that came to be called "wingback" (WB). Formations with one or two wingbacks came to be called single- or double-wing formations. Over time, the typically fast back who played fullback, on offense and defense, was replaced by a heavier one who presented a greater threat to run with the ball more or less straight ahead, and to tackle his opponent trying to do the same. For this purpose, the player tended to be placed closer to the line than previously—often as far forward as the halfbacks (the offensive backs then forming a letter T, sometimes called a "straight T", later to distinguish it from slight variants wherein other backs did not form a line perpendicular to that from the quarterback) or even farther forward. But the position kept being called "fullback". On defense, this necessitated another position name for the fast back who played farthest back. The phrase "goal-tend" was used for a time near the start of the 20th century before settling upon "safety man" or simply "safety" (S),