the players in those positions are allowed to make, during and preparatory to their team's snapping the ball. At the time they snap the ball, the team is required to have seven players (minus any number their side is playing short in Canadian football) on their line of scrimmage, which includes split or tight ends, but not flankers or wingbacks. Meanwhile, the distinction between fullback and halfback was erased, each replaced by "running back" (RB). That term became popular during the 1960s as well, although even into the 1970s, some playing the pro set kept the HB-FB distinction. So, for instance, in the flank formation shown above, those positions were named as in the straight T, while in the "split" version of the deuce backfield, the fullback occupied the other halfback position shown in the straight T. The distinction referred to the build of the players, the fullback being a stronger runner more or less straight ahead, and the halfback faster to attack the defense's flanks. However, on many teams there was no strong distinction between those backs, and since their major role was running with the ball, "running back" was most descriptive without maintaining a spurious geometric connotation that'd become outmoded by their lining up in different depth relationships. Alternative names for RBs are "deep backs" and "setbacks", although the latter is disfavored because it has also been used for backs in general, both on offense and defense. There is, moreover, a generic term for the deeper-playing backs (CB & S) on defense: "defensive back" (DB), appropriately enough. The term excludes the linebackers, even though they be backs in the traditional sense because they are usually not on their team's line of scrimmage. There also exist the generic terms "defensive lineman" (DL) and "offensive lineman" (OL), although the latter refers only to the interior linemen, excluding the ends because of their eligibility to receive forward passes. However, to this day many teams maintain the offense's fullback-halfback distinction, especially in "full house" backfields, i.e. those with a quarterback and three running backs, that is, no backs playing wider as wingbacks or flankers. This is confusing enough, when the fullback plays slightly forward of the halfbacks, as in the Y formation shown below, later used to run the wishbone system (the backs forming a letter Y or a resemblance to a wishbone): E T G C G T E QB FB