You shouldn't throw rocks.
Barry wants to practice pitching for the baseball team, but doesn't have a ball.
Barry wants to improve his throw,.
Barry ignores the stone and instead goes to a neighbor to ask to borrow a baseball.
Barry uses a stone as a baseball and when he throws it he pulls a muscle.
Barry practices his throw all afternoon and performs great at his next team practice.
Barry can't play on the team with an injury.