Scrabble of points for each lettered tile is based on the letter's frequency in standard English; commonly used letters such as vowels are worth one point, while less common letters score higher, with Q and Z each worth 10 points. The game also has two blank tiles that are unmarked and carry no point value. The blank tiles can be used as substitutes for any letter; once laid on the board, however, the choice is fixed. Other language sets use different letter set distributions with different point values. Tiles are usually made of wood or plastic and are square and thick,
Tile tracking the tiles are played is a standard feature of tournament play. Tracking sheets come in many varieties, and are often customized by players in an attempt to make the manual process of recording, tracking and counting tiles easier, more intuitive, and less prone to error. Accurate tile-tracking depends upon knowing the total letter distribution and letter frequency of the game and then reproducing each tile in its correct frequency to facilitate the "accounting" of each letter as tiles are played. Pre-printed forms are popular for Scrabble games because they eliminate the need to continuously create such a list for each