First off, you'll learn the umps strike zone very soon in the game. If you can get really low, and I always trained my catchers to be as low as they could be, on their insteps, butt almost touching dirt, then a low pitch may come right to the mitt. If you have to cherry pick or turn the glove down, its probably a ball anyway, and you may be waisting your time trying to frame a pitch below the strike zone.