{"schema":"chessgrammar_motif_entry/1","slug":"pin","name":"Pin","aka":"absolute pin · relative pin","category":{"key":"constraint","label":"States"},"edition":{"version":"v3.0","year":"2026"},"certified":true,"canonical":"https://chessgrammar.com/motifs/tactics/pin","tabs":{"identity":"https://chessgrammar.com/motifs/tactics/pin#identity","structure":"https://chessgrammar.com/motifs/tactics/pin#structure","examples":"https://chessgrammar.com/motifs/tactics/pin#examples"},"citation":"ChessGrammar (2026). Pin. In: ChessGrammar: A reference for chess concepts, Tactics grammar, edition v3.0. Entry cg:pin@1. https://chessgrammar.com/motifs/tactics/pin","variants":["bishop","counter","cross","cross_queen","last_rank","partial","queen","rook"],"seeAlso":["skewer","discovered-attack","battery"],"definition":{"id":"cg:pin@1","statement":"A sliding piece attacks a piece that, if it moves, exposes a more valuable piece of the same colour, or the king, directly behind it on the same line. This restricts the front piece to that line.","predicate":["A sliding piece (bishop, rook, or queen) attacks a target through exactly one piece of the target's own colour standing between them on the same rank, file, or diagonal.","The target is worth more than the screen, or the target is the king. If the screen is worth more than the target, the same three pieces form a Skewer instead. If the two are equal in value, neither motif applies.","The pin restricts the screen piece's movement. At least one otherwise-legal move of the screen would leave the line. A position where the screen already has no such move, for example a pawn with no capture to make, is not counted as a pin. The pin must explain a real restriction. Coexisting with one is not enough."],"diagnosis":"Pin differs from Skewer by which piece the line constrains and exposes. In a Pin, the less valuable front piece cannot move without exposing the more valuable rear piece. In a Skewer, the more valuable front piece must move and expose the rear target. In the counter-example shown here, no piece stands between rook and king, so the position is an open-line check that is neither motif.","maturity":{"state":"stable"},"holotype":{"fen":"4k3/8/8/8/4n3/8/8/R5K1 w - - 0 1","move":"a1e1","san":"Re1","pinner":"e1","pinned":"e4","shield":"e8","why":"The rook moves to e1 and attacks the knight on e4, directly in front of the black king on e8 on the same file. The target is the king itself, which always counts, so no value comparison is needed. Every move the knight could otherwise make leaves the e-file, so the pin is real. That is exactly an absolute pin."},"nearMiss":{"fen":"4k3/8/8/3n4/8/8/8/R5K1 w - - 0 1","move":"a1e1","san":"Re1+","delta":"The knight moves one square off the e-file, from e4 to d5, before White plays the identical Re1.","why":"The knight is off the file, so no piece of the king's colour stands between the rook and the king on the same line. The file is open, and Re1 is now a check and not a pin. What changes is whether a piece stands in between at all. No comparison of values is involved.","neighbour":"none"},"nearMissPending":null,"standing":{"certified":true,"scope":"definition"}},"axes":[{"key":"kind","name":"The pin's target relative to the king","values":["absolute","relative"],"nature":"partition","note":"Absolute: the target is the king itself -- always significant, no value comparison possible. Relative: the target is not the king, and is only worth naming when it outranks the pinned piece. This is a genuine partition -- every pin carries exactly one value -- but it is folded into the base pin occurrence rather than shipped as a separate named variant. Included here for completeness, not because a separate entry exists for it below."},{"key":"relation","name":"Additional conditions on a pin","values":["partial","cross_queen","cross","counter"],"nature":"facts","note":"Unlike kind (and unlike skewer's screen and direction axes), this is not a partition: partial, cross and counter are independent facts layered on top of the base pin, and a single occurrence can carry more than one, or none. Partial reads the pinned piece's own line of movement; cross and counter read the relation between two separate pins, not a property of one. Cross queen is the strict specialisation of cross (same relation, with the piece behind the pin being a queen), grouped on this axis specific-before-generic."},{"key":"pinner","name":"The piece executing the pin","values":["queen","rook","bishop"],"nature":"partition","note":"An exact partition, with named values -- the mirror image of kind, which is a partition without them. The pinning piece is always a sliding piece, so it carries exactly one of three possible types: queen, rook, or bishop. Because this axis is a genuine partition, it behaves like skewer's axes and unlike relation: a near-miss that swaps the pinner's type routes to the sibling value (queen to rook, bishop to queen), never to the plain motif entry -- the only pin axis with that property. It reads only the pinning piece, never the pinned piece or a second pin. Literature caution, worth flagging plainly: the same word names two different roles two axes apart -- queen here names who pins, while cross queen on the relation axis names the piece behind the pinned piece."},{"key":"pinned_geometry","name":"The pinned piece's own geometry","values":["last_rank"],"nature":"facts","note":"A single-value axis, an independent fact about the pinned piece: it is a pawn of the victim's side standing on its own seventh rank, one step from the promotion the pin denies it. Not a partition -- most pins carry no value here at all -- so losing it falls back to the plain motif entry, like the relation values. It reads the pinned piece, while the pinner axis reads the pinning piece -- the two stack freely (the reference position below carries both bishop and last rank). It is a geometric fact about one pin, never a relation between two separate pins."}],"summary":"A piece is restrained because moving it would expose a more valuable piece, or the king, behind it on the same line."}