With the later reduction in sides from 14 to 12 players, and introduction of the thrown (not 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 USA 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 USA version, there is no necessity that the player who snaps the ball have equal numbers of teammates flanking him or her on the line.