The 4 attackers stand in a square (near the hats) around the post,
the 4 defenders are holding the post with one hand.
The 9th person (the declarer) stands with the ball outside the square of hats.
The declarer brings the ball to one of the attackers, the defender facing the attacker who receives the ball has to run for the hat while the attackers now have to score as fast as possible.
If all goes well, the attackers quickly find the free person because one of the defenders has to run around the hat.