ISTANBUL (AP) — Referees at the Under-20 World Cup now have another tool to keep wayward players in line.

FIFA announced Saturday that referees at the 24-team tournament in Turkey are using vanishing spray for the first time. It marks a white line on the grass where teams defending a free kick must stand — stopping the defensive wall moving forward or changing the angle of the free kick.

The spray, produced by Argentine company Fair Play 9.15 Limit, is non-contaminating foam that can be used on grass, synthetic and dirt pitches. It disappears between 45 seconds and two minutes of being applied and will be used on a trial basis in all 52 matches of the tournament.

FIFA spokesman Wolfgang Resch said it was used "several times" during the four matches Friday.