This drill corrects a long or loopy swing and will help the player increase the barrel's velocity at impact with the ball.
Batter should stand facing the fence.
Take an old bat, put the handle against your chest, and extend the barrel tip straight out... level with the ground.
Move your body so that the end of the bat barrel just touches the fence with the knob on your chest.
Here is the test: You should be able to swing the bat from that position WITHOUT hitting the fence. If you are hitting the fence, you are not getting the knob of the bat through the swing first. The knob comes through, then the barrel.