File

A file contains eight squares in a vertical direction. The files of the board are labeled a, b, c, d, e, f, g, and h from White's left. Those letters remain fixed: from Black's side the a-file appears on the right, but it is still the a-file.

The file letter forms the first part of every square coordinate. In e4, e identifies the file and 4 identifies the rank.

A rook moves along files and ranks, while a queen can use them as well. Neither piece may jump over an intervening piece. Pawns advance on their own file and capture onto an adjacent file.

Open and semi-open files

• An open file contains no pawns from either side.
• A file is semi-open for a player when that player has no pawn on it, although the opponent may have one.

These labels matter because rooks and queens often use lines without friendly pawns to enter the opponent's position. A file containing pawns from both sides is not open; it may be called closed, especially when the pawns block each other, although that usage is less exact.