An open file is a file that has no pawns on it. Either player can place a rook on an open file to control all of the squares on that file.
A half-open file is a file that has pawns of only one color on it. A player can place a rook on a half-open file to control all of the open squares on that file and attack the opponent’s pawn.
Rooks are usually more powerful on open files and on half-open files than they are on closed files. Put your rooks on open files. Rooks on open files control more squares and they can use those squares to attack and defend.
An open file is even more valuable when you can use it to invade into the opponent’s territory. To invade on an open file, you need to have an entry point for your rook. An entry point is a square deep in the opponent’s territory where you can safely move your rook. Without an entry point, there may be no way to use the open file.
Sometimes, if you do not have an entry point, you can make one. Then you can use the entry point to invade deep into the opponent’s territory, usually on the seventh or eighth rank. Once your rook invades the seventh or eighth rank, you can move it sideways to capture pawns or launch an attack.
From the book, “TOTAL CHESS: Learn, Teach and Play the Easy 1-2-3 Way,” by John Herron
TOTAL CHESS is your complete guide to chess. It covers everything: rules, strategies, tactics and checkmates.
Everything in chess comes in threes. Three simple strategies are presented for the opening, midgame, endgame, etc. Each lesson is brief and covers one concept in simple language that everyone can read and understand.