The rules of football give the problem its dimensions. For a direct free kick the wall must stand at least 9.15 m (10 yards) from the ball. The goal is 7.32 m wide and 2.44 m high. A wall of players is typically about 1.8–1.9 m tall, and they can jump. So the ball has to clear a high obstacle close by, then still come down under the bar.