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,
Dominoes artist who toppled the first stone was the Finnish acrobat Salima Peippo. At one time, Pressman Toys manufactured a product called Domino Rally that contained tiles and mechanical devices for setting up toppling exhibits. In Berlin on 9 November 2009, giant dominoes were toppled in a 20th-anniversary commemoration of the fall of the Berlin Wall. Former Polish president and Solidarity leader Lech Wałęsa set the toppling in motion. Since April 2008, the character encoding standard Unicode includes characters that represent the double-six domino tiles in various orientations. All combinations of blank through six pips on the left or right provides