When his own side have the ball the guard must block sharply until the quarter has time for receiving the ball, and, at any rate, beginning the motion of the pass. It is safer, in the case of inexperienced guards, to tell them to block until the quarter has time to get rid of the ball. The distinction is this: that an experienced guard sometimes likes to gain just that second of time between the beginning of the pass and the completion of the swing, and utilize it in getting down the field or making an opening. So accustomed does he become to measuring the time correctly that he will let the opponent through just too late to reach the quarter, although it seems a very close call. It is not safe to let green guards attempt anything so close. They must be taught to block securely until the ball is on its way to the runner or kicker. The blocking of a guard is much less exacting in its requirements than that of the tackle. Not that he must not block with equal certainty, but the act requires no such covering of two men as often happens in the case of a tackle. The guard forms closely towards the centre, and then follows his man out if he moves out, but only as far as he can go, and still be absolutely certain that the opponent cannot pass between him and the snap-back. To be drawn or coaxed out far enough to admit of an opponent's going through the centre shows woful ignorance in any guard. [Illustration: V. M. HARDING. Harvard.] When a kick is to be made the blocking must be prolonged a little, and on a drop-kick (as mentioned earlier) it should last until the ball goes from the foot. When blocking for a run, of course much depends upon where the opening is to be made, and a guard must be governed accordingly. The method itself is, again, different in the guard from that exhibited in the tackle. A guard may not move about so freely and must face his man more squarely than a tackle, for the guard must protect the quarter first, while the tackle considers the half only. If a guard allows his opponent to get a fair lunge with outstretched arm over or past his shoulder, he may reach the quarter's arm even though his body is checked, while such a reach at the point in the line occupied by the tackle would be of no value whatever. Previous to the snap-back's playing the ball it is the duty of the guards to see that their individual opponents do not succeed in either kicking the ball out from the snap-back's hand or otherwise interfering with his play. This is quite an important feature, and a centre should always feel that he has upon either hand a steady and wide-awake assistant, who will neither be caught napping nor allow any unfair advantage to be taken of him. The guard should bear in mind one fact, however, and that most clearly. It is that squabbling and general pushing about are far more liable to disconcert his own centre and quarter than to interfere with the work of the opponents. THE CENTRE, OR SNAP-BACK