Take turns adding dominoes. Using your hand of seven tiles, add one domino to either narrow end of the first domino. You can only add a domino to the board if it has a number that matches a number on one open end of the domino board. For example, if the first tile is a pair of 4s, you can only play a domino that has one end marked with a 4. Place the dominoes together end on end to show that they are matched.