On a grass pitch, the bowler creates a rough patch where he lands his foot and follows through after delivering the ball. The rough patch can become cratered and becomes more abrasive as the match continues and more people step on it. The abrasive surface means that the ball will increasingly grip more if it lands in the footmarks. Bowlers, particularly spinners, will aim the ball there as it will turn more sharply, and is more likely to get irregular bounce from such areas, making it more difficult for the opposition batsmen.