Dominoes spots from one to six are generally arranged as they are on six-sided dice, but because blank ends having no spots are used, seven faces are possible, allowing 28 unique pieces in a double-six set. However, this is a relatively small number especially when playing with more than four people, so many domino sets are "extended" by introducing ends with greater numbers of spots, which increases the number of unique combinations of ends and thus of pieces. Each progressively larger set increases the maximum number of pips on an end by three, so the common extended sets are double-nine, double-12,
42 (dominoes) in some variants, three) marks are bid and the bidder must have four doubles. Jump bids are allowed for Splash and Plunge. All tricks must be won for a successful plunge bid. If the opponents win even one trick the plunge bid fails and the opponents get the marks. Another less common rule is to allow a player to bid Sevens. Instead of the highest domino winning each trick, the domino whose sum is closest to seven wins. Dominoes are classified as "sevens" (the 4-3, 5-2, and 6-1), "one away" (dominoes adding to six or eight), "two away" (adding to