Why a rook wants the seventh rank

The seventh rank is where your opponent's pawns started and never left, and the eighth is where the king is standing. A rook that gets there attacks both at the same time.

Worth about an extra pawn
Two of them are called pigs
Reached through an open file

A rook on the seventh rank is worth roughly a pawn more than the same rook anywhere else, and it is worth it for two reasons at once. Every enemy pawn that has not moved is standing on that rank, undefended by anything except pieces. And the enemy king, if it has castled and not made luft, is stuck on the rank behind it, unable to come out and defend anything.

It is the same rank whichever colour you are: your seventh is the rank your opponent's pawns start on, which is rank 7 for White and rank 2 for Black.

Two rooks on the seventh: the pigs

Both white rooks are on the seventh, so the black king has no square on it and cannot come out. Black's own rook is busy.

1.Ra8#

Checkmate, delivered on the eighth rank and made possible entirely by owning the seventh.

Doubled rooks on the seventh are called pigs, because they eat everything. They are also, in a lot of positions, worth more than a queen: they cover the entire rank between them, they defend each other, and the defending king cannot approach either of them. If you can get a second rook to the seventh, the usual advice is to stop counting material and start looking for the mate.

Getting there is the hard part. A rook reaches the seventh through an open file, so the seventh rank is normally the reward for winning a file first, usually with a battery.

Why it matters more in a rook endgame

Both sides have a rook and three pawns. White's rook is on the seventh and Black's is not, and in a rook endgame that is most of the difference between the two positions.

In a middlegame the pawns on the seventh have pieces defending them. In an endgame they have the king, and the king is the piece your rook has just cut off. That is why an active rook is the single most repeated instruction in rook endgames, and why giving up a pawn to get your rook behind your opponent's is usually a good trade rather than a desperate one.

The other half of the same idea is that a rook on the seventh is a reliable way to draw a position you are losing. Checks along the seventh with a king that cannot escape forwards give perpetual check more often than any other endgame resource.

Black to move. Both rooks are already on their own seventh rank. White has just pushed the f-pawn, which was a mistake.

Show the answer

40.f5 40...Rxg2+ 41.Kf4 41...Rxg7

The line ends with the pattern paying off in material. The position is from a real game on Lichess, rated 610 in their puzzle pool, and it is one of the positions in the Skewers skill in the trainer.

Get there with a tempo. A rook that arrives with check, or attacking something, does not give your opponent a free move to organise.
A rook on the seventh plus a threat on the back rank is the standard combination. Neither is usually enough alone.
If your opponent's rook reaches your seventh, look for a way to block the rank rather than chasing the rook. Pawns on the seventh cannot be saved one at a time.
In an endgame, a rook behind a passed pawn beats a rook on the seventh. That is the one common exception.

Questions people ask

Why is a rook on the seventh rank so strong?

Because it attacks the pawns that have never moved and traps the king on the back rank at the same time, and those two jobs happen to need the same square. A rook on the seventh usually wins a pawn or two by force, and the king cannot help, because coming forward to defend means walking onto the rank the rook controls.

What are pigs on the seventh?

Two rooks doubled on the seventh rank. The nickname is old and the reasoning is that they eat every pawn on the rank. They defend each other, so the enemy king cannot approach, and together they take away the whole rank, which frequently turns a normal position into a forced mate on the eighth.

Seventh rank sits under Pieces and squares in the reference. Nearby: