2d 20D20s are used for resolving skill tests, and for rolling on certain large tables. Often, two or more d20s will be required. This is noted as Xd20, where X is the number of dice to be rolled.D20s are used for resolving skill tests, and for rolling on certain large tables. Often, two or more d20s will be required. This is noted as Xd20, where X is the number of dice to be rolled.