A runner scores through successfully moving around all the bases and crossing home plate without being put out. Scoring is usually the result of a combination of walks, base hits, or sacrifices; skillful base running; or errors by the defensive team. Sometimes the batter circles the bases on one hit. This is known as a home run. A batter usually scores a home run through hitting the ball over the outfield fence. The batter might round all four bases without hitting the ball over the fence, but this occasion is rarely found in the baseball game. This play is known as an inside-the-park home run. If there are base runners at the time the home run is hit, those players also round the bases and score. The team at bat scores four runs if there are base runners on all three bases while the batter hits a home run, and the play is called a grand slam.