How do I handle a line call appeal?

Only rally-ending shots can be appealed, and any player may appeal. The appeal must come before the next serve is hit; for a match-ending shot, before the scoresheet is initialed (Rule 19.D).

Without line judges:

• If you clearly saw where the ball landed, you must make the call (Rule 19.E).
• If you can't make a call, the player's call stands, unless the player asked the opponent and the opponent made a definitive call, in which case the opponent's call stands (Rule 19.G.1).
• If neither the players nor you can make a call, the ball is in (Rule 19.G.2).

With line judges:

• If you can't make a call, the line judge's call stands. If neither you nor the line judges can call it, replay the rally (Rules 19.G.3, 19.G.4).
• If a line judge signals blocked or blinded, make the call immediately if you saw it; on a rally-ending shot you can't call, canvass the other officials (Rule 19.H).

After appealing or asking the opponent, a player's team loses the right to make that call, except to override it in the opponent's favor (Rule 19.D.3).