A foul goes in, the crowd shouts, and the referee... doesn't blow. Arms out, "play on!", and the attacking team carries on with the ball. To the touchline, it can look like the referee has missed it. In reality, it's one of the most skilful calls in the game. Get it right and nobody remembers it. Get it wrong and you've punished the team that was fouled. Here's how advantage works, when to use it, when to leave it, and what to do when it involves a red card. 1. The basics Law