side) as in a balanced line, leaving the tackles together. In the bottom illustration, the guards are kept "inside" by being next to each other. The end positions are fixed by rule, because "end" is a rule book term. As to the backfield, the top illustration preserves the principle of the names, reflecting distance from the line. However, the bottom illustration needs further explanation, having eliminated the halfbacks and introduced a new position name, "tailback" (TB). Wingback has been described above, but the "WB" in the above illustration is deeper back than that position name would seem to warrant. That is because this is a "wingback deep" version of the single wing, and the position is named wingback because the player is named for his true wingback position as it exists in other versions. In this version the player may stand as deep as any other back, but there has been a reluctance to identify formations in American football as having more than one fullback (or tailback—see below), although two-fullback systems were not uncommon at one time in rugby. What to make of the replacement of the other halfback from the top illustration by the fullback in the bottom one? Well, if the wingback were playing in a true wingback position but named halfback, then the other "halfback" would be playing deeper and thus deserve the name fullback. Another justification is that the player positioned as the left halfback in the top illustration tends to have the fullback characteristics described above. But rather than call the faster, lighter back behind (and in this formation, to the left of) him a halfback and so contradict the distance-back-determines-the-name principle (and rather than add rugby's three-quarters back), we call that player "tailback"—the tail of the formation, farther back than the fullback. Even when two players positioned to take a thrown snap in a single wing formation are level with each other (i.e. at equal depth), the faster one (usually playing weak side) is often called the tailback and the more massive one the fullback. The quarterback in this formation is not in position to receive the snap. ASCII art (letter diagrams) cannot show this fine a detail, but a quarterback in position to take a handed snap is allowed by rule to stand farther forward, in a place which would otherwise cause illegal confusion as to whether the player was in the backfield