American handball, known as handball in the United States and sometimes referred to as wallball, is a sport in which players use their hands to hit a small, rubber ball against a wall such that their opponent(s) cannot do the same without the ball touching the ground twice or hitting out-of-bound. The three versions are four-wall, three-wall and one-wall (also known as Wallball or international fronton). Each version can be played either by two players (singles), three players (cutthroat) or four players (doubles), but in official tournaments, singles and doubles are the only versions played.