To help develop the players’ quickness in turning their body around for the ball. The purpose is also to emphasize getting their head and shoulder around quickly.
One wide receiver lines up about ten yards from a coach with his back to the coach.
The coach then throws the ball toward the players and when the ball is halfway to the player the coach says “Left” or “Right”. The player turns as quickly as possible and tries to catch the ball in his hands.
Using the same procedure as above, the player turns just his head and shoulders around as quickly as possible.
Both can be done also with the firing squad drill setup with more than 1 wide receiver, and instead of the coach it could be as well a quarterback throwing the ball.
Emphasize quickness to turning body or head and shoulders around and catching the ball with the hands.