In tennis, a Cross-over occurs when a player steps onto their opponent's side of the court.
This usually happens after a point ends. Players might cross over to check a ball mark on clay courts. They do this to see if a close call is correct.
Cross-overs can be friendly or confrontational, depending on the situation. In professional matches, crossing over without permission can result in a penalty.
Players should ask the umpire before crossing the net. Rafael Nadal is known for occasionally crossing over to check marks on clay courts. Cross-overs are more common in casual matches without officials.