Invisible ink marked domino
In blocking game, the most basic domino variant is for two players and requires a double-six set. The 28 tiles are shuffled face down and form the stock or boneyard. Each player draws seven tiles; the remainder are not used. Once the players begin drawing tiles, they are typically placed on-edge in front of the players, so each player can see their own tiles, but none can see the value of other players' tiles.
But what if you can see the pips from the back? You can see the value of other player's tiles. Stop hesitating, invisible marked domino can really do this for you, to see other player's tiles just from the back of the domino.