Tiddly-Wink is a member of the Block game family which is suitable for a larger number of players. However, there are several different games with this name which have the common feature of allowing an extra play after setting a double. Here is the version given in American sources.
This version uses a double six set and five to eight players. You will also need poker chips or other counters.
The size of the hand is always three tiles. The rest of the tiles stay in the boneyard and are not used in the round.
Each player puts up a stake in a pool for the round. The player with the largest double always leads and play continues clockwise around the table. If nobody has a double, then a tile is drawn from the boneyard and the highest end is the lead.
The unique feature of the game is that If a player has a double, he turns it in line and has the option of playing a second tile in his turn.
After the first tile, players have to add tiles to only one end of the train that starts from the lead. If a player cannot play, he passes. The hand stops when one player dominoes or when nobody can play.
The player who dominoes wins the pool. If nobody dominoes, then the player with the smallest total of pips in his hand wins the pool.
"Tiddle-a-wink" is the British or Euopean name for a variation for six or more players, which uses a double nine or double twelve domino set.
The size of the hand is an even distribution of all the tiles to each player, which will vary with the number of players and the set of the domino set used. The rest of the tiles stay in the boneyard and are not used in the hand.
The rules and strategy are the same as the American game. This game improves with more players, however. With fewer players, the larger boneyard means that it is harder to domino so most games are settled by blocking instead.
The more of the tiles that are out of the boneyard (i.e. the more players) the better the game. A lot of winning in this game is the luck of the draw. A double and a tile in the same suit will allow you to get rid of two tiles in one play, but only if you can play them before someone else dominoes. The real trick is to have the lowest score, which is not the same thing as having the fewest tiles left in your hand.