Before this drill, Tod Mattox addresses the entire team and says he wants calmer platforms in serve receive. He talks specifically about the technique for passing serves that are up high.
The drill requires players to pass balls hit by Mattox off a box from the other side of the net. As you'll see, he continually reinforces a couple of key points: "Calm" and "shoulder down and hold it."
On the other court, players pass easier balls off tosses to get their technique right.
