Seven-ball is a contemporary rotation pool game with rules similar to nine-ball, though it differs in two key ways: the game uses only seven object balls as implied by its name, and play is restricted to particular pockets of the table. William D. Clayton is credited with the game's invention, ca. the early 1980s.
At the start of the game, balls one through seven are racked in a hexagonal configuration, with the 1-ball placed at the rack's apex, centered over the table's foot spot, the 7-ball placed at the rack's center, and all other balls placed clockwise (see photo top right). Immediately following the break shot, the opponent must elect three pockets along one of the table's long rails. Once that selection is made, that player may only legally pocket (pot) balls in the selected pockets, and the player who broke is automatically assigned the three pockets situated along the opposite long rail. Balls must be pocketed in rotation, starting with the one, as the object ball. Balls pocketed via combinations off of the object ball are legal. No points exist for any balls. The 7-ball must be pocketed in the called side to be a legal win. Scratches on any object ball allow the opponent ball-in-hand, but the sunk ball remains potted. Scratching on the 7-ball is a loss. Pocketing the seven in any other pocket than the called side results in ball-in-hand to the opponent, and a spotting of the seven.
A special 7-ball was designed for television matches by Charles Ursitti (billiards historian, referee and Willie Mosconi's one time manager) to address the problem that the color of the seven and three balls in a standard set of pool balls are nearly indistinguishable when viewed on a TV screen. The ball adopts the stripe of the 9-ball with the color of the solid black 8-ball, the "money balls" of their respective namesake games. A similar effect can be achieved with a standard 15-ball set, substituting the striped 15 for the seven, after which, on coin-operated tables, a second game may then be played with the striped 9 to 14, and the solid seven as the money ball.
If a ball is potted when a penalty has been conceded, the offending player's ball which has been potted is to be placed once again back into the original spot it was at before as it was an illegal pot. This is the same rule as in snooker.
The original informal incarnation of seven ball led to a variant professional ruleset that enjoyed a brief heyday[clarification needed] in the Sudden Death Seven-ball series of pro tournaments, broadcast on the American cable TV network ESPN.
As illustrated to the left, a regular set of pool balls and a nine-ball diamond rack turned sidewise are adequate.
When racking with an eight-ball triangle rack simply place an extra ball at the top of the triangle and remove along with the rack.
The term 'seven ball' also refers to a complete whitewash where a weaker opponent is outclassed by a more skilled player.