The Blank Tile
The game has two blank tiles that are unmarked and carry no point value. The blank tiles can stand in to be any letter. Once laid on the board, the choice of the letter that it stands for is fixed until the end of the game. If a blank tile is placed on a double-word or triple-word square, it causes the corresponding scoring to be applied to the word or words that are created as a result. As of 1976, the official rules state that if you draw the blank tile before the start of the game to determine who goes first, that blank tile beats an “A.” The object is to draw the letter that is the closest to the beginning of the alphabet to go first. If you draw the blank, you can go first. If two players each draw a blank, then the tiebreaker is for each of those two players to draw another tile.
Forbidden Moves
Although some players use house rules to govern the blank tiles, the official rules of Scrabble do not allow you to do two things.
You cannot replace a blank tile with the letter it represents so you can use the blank in another word.You cannot change the letter a blank tile represents.
At official tournaments, these rules are strictly enforced. To avoid any confusion, the National Scrabble Association recommends that both players make a note of what letter a blank tile represents when it is played.