Valve

A valve is a chess-problem device in which one piece moves along a line, opening that line for an attack or mate while simultaneously closing a different line.

Category
Tactics
Difficulty
Intermediate
Also known as
line switch, switch

Valve is a device used in chess problems in which one piece moves along a line, opening that line for an attack or mate while simultaneously closing a different line.

The moving piece functions as a switch. Before the move, both lines are either blocked or open in ways that prevent the desired effect. After the move, one line becomes available for the attacking side while the other is cut off, blocking a black defence or escape route.

Club players encounter valves most often in direct-mate problems and helpmates. A typical case involves a white rook or bishop that must leave a file for its own queen while occupying a diagonal that stops a black piece from defending. The single move therefore performs two opposite tasks at once.

Because the same square serves two conflicting purposes, valves demand exact timing and placement. Solving problems that contain a valve usually requires identifying which piece can reach the critical square without disturbing the rest of the position.

Key takeaways

  • A valve is a problem device in which one piece moves to open a line for an attack while closing another line at the same time.
  • The moving piece acts as a switch that enables a mate or check on one route and blocks an opposing defence on the other.
  • Valves occur mainly in direct-mate problems and helpmates that demand exact timing and placement.
  • They reward positions where a single square lets one piece perform two opposite functions without disturbing the rest of the setup.

Frequently asked questions

What is a valve in chess problems?
A valve is a device in which one piece moves along a line, opening that line for an attack or mate while closing another line at the same time.
How does the moving piece function in a valve?
The piece acts as a switch that enables one line for the attacking side and blocks a defensive line, performing two opposite tasks with a single move.
In which types of problems do valves most often appear?
Valves appear mainly in direct-mate problems and helpmates that require exact timing and precise piece placement.
Why do valves reward careful solving?
They reward positions where one square lets a piece open a needed line and close an opposing defence without disturbing the rest of the setup.

See also

  • Battery — A battery consists of two or more same-colour pieces aligned on a file, rank or diagonal, with the stronger piece behind, so the front unit can move to unleash the rear piece’s concentrated pressure.
  • Chess Problem — A chess problem is a composed position in which the solver must find a precise sequence of moves to achieve a stipulated goal, most often checkmate in a set number of moves.
  • Clearance — Clearance is a tactical motif in which a piece moves aside to vacate a square or open a line for a more powerful piece—usually a rook or queen—often gaining tempo by delivering check or creating a threat.
  • Discovered Check — A discovered check occurs when one piece moves aside, revealing an attack on the enemy king from a second piece positioned behind it on the same line.
  • Discovery — A discovery is a tactic in which one piece moves off a line, uncovering an attack from a second piece stationed behind it.

Written by Chesswick.

Reviewed by Maria Russell.

Published
Last updated

About the reviewer

Maria Russell

Maria didn't grow up dreaming of chess. She grew up dreaming of getting through bedtime without a meltdown, and chess just happened to be the thing that worked.

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