What it is
The back hand throws the barrel of the bat straight to the ball and through the ball. If the ball was a nail and the bat was a hammer, you are throwing the barrel head to the ball. At contact the back arm is bent — like the arm position before throwing an uppercut — and extension comes AFTER contact, with the ball on the barrel as the back hand throws the barrel through it.
Why it matters
That is the main purpose: getting the barrel to the ball with the back hand is how you swing with purpose and make hard contact.
What to look for
The barrel getting to the ball instead of dragging through the zone. The barrel is the tell for the back hand — you do not need to see the hand itself.
How to do it
When the barrel is dragging, use the wrist like using a hammer: the wrist throws the head of the bat to the ball — while the bottom hand is simultaneously throwing the knob. Neither action happens first; together they make the swing.
What good looks like
Contact with the back arm bent, then extension through the ball.
Train it with Coach Bass
Drills for this