I always hear pitching coaches at the younger ages telling their pitchers to snap down. Does this actually help you?
your supposed to keep your palm up on a fastballso idk
Well , if your looking for a downward action, duh, you should snap down.
But if your trying to just throw a fastball to locate, just keep your palm
up just like kelvinp said.
Unless some other context is provided, I would be wondering what the issue is for which "snapping down" would be the fix.
I doubt that this would be considered a "teach" in most circles. I did teach this to my son to encourage a good finish and to increase the backspin on the ball.