The main work of the guards may be summed up as blocking, that is, guarding; making openings for the passage of the runner whenever certain signals are given; running behind the line to interfere for the man with the ball; running with the ball occasionally; breaking through the opposing line to interfere with the quarter-back in passing the ball; and tackling the runner or stopping a kick. The guards and the center have the most laborious work on the eleven, if they do their duty, for they practically have no respite from hard work. They must bear the brunt of the heavy plunging of their opponents through the center, and at the same time struggle to break through the opposing line, which is doing its utmost to prevent them. They must do this without a letup just as long as the other side has the ball, and, moreover, in that part of the line which is most compact. Then, when their own side has the ball, they are expected to use their strength and wits from the moment the ball is put in play until it is again down, in blocking, making openings, and in interfering for the player who is attempting to run. Further, they have little time to catch their wind, for almost the first point which should be drummed into them by the captain or coach is to be always on hand the moment the ball is down, to make or prevent a quick play. It can be truly said that no team is well trained until the center part of the eleven, as indeed the whole team, is prompt on this point. While the guards have all this hard work, they seldom have a chance to distinguish themselves, either by a run, a clean tackle, or a fine interference which is apparent to the untrained eye of the spectator. On the other hand, it does not take much yielding at the center to bring forth the criticism that that part of the line is weak.

On account of the nature of their work, the guards should be large and powerful, like the center. It is even more necessary that they should be quick, agile, and swift, than the center, because the guards should always go through the line when the opponents have the ball. On their success in doing this largely depends the strength or weakness of the team's defense.

The chief point in defensive play is to tackle the runner before he reaches the line, and the guards are large factors in doing this. Unless this is done, the ball can be steadily carried down the field when not lost by a fumble, for any team is able to gain five yards in three consecutive trials when the runner is allowed to reach the line each time before being tackled. Any means, therefore, which the guards can employ to interfere with the quarter-back before he has passed the ball, or the runner before he has reached the line, should certainly be used. All the strategy and tricks known in wrestling which can be applied to the situation should be eagerly sought and practiced. The great point to remember is to apply the power quickly and hard, to summon all the strength for the initial effort, and to work desperately until free from interference. Only by doing this can the guards hope to break through and secure the quarter-back or runner behind the line. Slow pushing, however powerful, will accomplish little. If held in check until the runner and the pushers strike the line it is only a question of how many yards the runner will gain before the mass breaks and falls forward.

In applying his power the guard, as well as his companion rushers, has an immense advantage in being permitted to use his hands and arms freely in getting his opponent out of the way. This enables him to put into practice all the skill he possesses in handling an opponent who is allowed to block only with the body. The guard also has another advantage in being free to move whenever he pleases, but he must remember that the opening for the runner may be made on either side of him and be careful not to give his opponent help in making it. It assists the guard greatly in breaking through if the tackle draws out the opposing line as much as is wise in a good defense. This separation should be wide enough to allow the players in defense to break through easily without interfering with each other. It is also usually helpful in breaking through to be restless, but cautious at the same time, in order not to give the opponent an advantage.

The guards and the tackles especially should watch for signs which shall indicate what the play will be, and then go through the line as low as possible for a tackle. They should break through to the right or left of their opponents as seems best at the moment. In order to break through quickly they must have their eyes on the ball when it is snapped and spring forward the instant it is put in play. Quick glances may be cast at the opponents while still constantly watching the ball.

The guards, with the center, are usually called upon to meet the heavy charges in the opening plays from the center of the field. These, as a rule, come in the form of wedges. Two points should be carefully regarded by these center men in attacking a wedge: first, to approach the wedge with the body bent in a position for greatest power and for meeting the wedge low down; second, to focus on the mass in such a way that it cannot break through between them without being separated, and so giving the guards a chance to tackle the runner. In doing this it should be the aim to focus as nearly as possible upon the point of the wedge, in order to check its advance and throw the forwards back on the runner. The runner will then be forced to come out, if he has not already become entangled in the mass. In making the attack the guards and center should run with dash and determination, at the same time watching closely for the runner and trying hard to tackle him.

Two successful ways of attacking a wedge have been originated. One member of the center trio will sometimes jump over the heads of the forwards and try to fall on the runner and thus secure him, or he will hurl himself headlong at the feet of the oncoming wedge and cause it to trip over him. To make either one of these attacks well the player must be perfectly fearless, and should also use good judgment. In the former case the player must time his jump and not land short of the runner, or he will be pushed quickly to the ground or carried along on the heads of the forwards; neither must he jump so far over that he will miss his man. If he throws himself in front of the wedge he should not do it too soon, lest the wedge will be able to avoid or step over him.