This drill is designed to quicken reaction time to grounders and line drives using lateral movement. We've been doing the following for several years with our summer 12 year old traveling squad.
At the end of each practice the entire team competes in a contest to see which player can keep the most out of ten balls from hitting a chain link fence at his back. The fungo hitter stands only thirty-five or so feet from the fielder. The fielder has 20 feet of fence to cover. The fence is 6 feet tall. We hit to the left and the right, up and down. The pace between fungos quickens. A clean catch is not necessary to score. The player need only keep the ball from hitting the fence to his rear. By the end of the summer players need from between 8 to 10 out of ten to win.
(PS. I caught for FSU from '59-61. Love to hear from anyone on that squad.