Referee Spray is a substance applied to an athletic field in order to provide a temporary visual marker for use by both players and referees for the purposes of ensuring fair play...
Referee Spray is said to help prevent unnecessary delays by preventing the defensive team from encroaching closer than the mandated 10 yards (9.1 m)...
The referee has full discretion on whether or not to use Referee Spray, and opponents are required to retreat 10 yards from the spot of a free kick regardless of whether Referee Spray is used (unless the team awarded the kick elects to take a "quick" free kick with opponents still within 10 yards).