The duties of the full back on the offensive are largely the same as those of the half back. The full back, however, on account of his position midway between the half backs and directly tack of the center, is better situated for line plunging than for runs around the ends, and it is here that he is usually called upon to advance the ball.
The full back is the battering ram of the eleven. He it is who is commonly the man projected into the mass of players in the center, and a player must have rugged endurance and ability to withstand the hard usage incumbent on a man who plays this position well and conscientiously. The full back is also often used in the interference, of which he is a member on practically every play when he is not carrying the ball. He must be strong, heavy and full of courage, ready to go up against the opposing line with an abandon that would be in evidence were there no line there at all. The important part which he has to perform in every play makes it imperative that he be a man of iron endurance and in perfect physical trim.
The full back must also be' a good kicker or else able to take the place of the man who does the kicking, when the time comes for such a play. The kicking must be done from the full back's position, and, if the regular occupant of the position does not do it, the full back should be able to take some other position to assist in strengthening the defense, weakened by the withdrawing of the kicker from his regular position.
On defense the full back is the final obstacle in the path of the enemy. He must guard his own goal, ready to tackle any hostile runner who has succeeded in evading the men in front of him. To do this he should assume a position 15 yards or so back of the line of scrimmage, following the plays from side to side and holding himself in readiness to get into the path of any runner who may break through.
The defensive full back must also be a man able to handle punts sent by the opponents. He must be a sure catcher and able to run back with the ball through an open field.