Undefended rook on the back rank under enemy pressure.

By Climbchess Research · 2026-05-08 · 3 min read · Updated May 8, 2026

SAE concept sae_6291 fires when undefended rook on the back rank under enemy pressure.. It appears in 5 of 9,950 Climbchess puzzles (0.1%), spanning ELO 1176–1401 (median 1176).

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This page documents Undefended rook on the back rank under enemy…, one of 4,505 interpretable chess concepts extracted from Leela Chess Zero via sparse autoencoders. The full feature description from our SAE labelling pipeline reads:

Undefended rook on the back rank under enemy pressure.

This pattern fires in 5 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 1176 to 1401, with a median rating of 1176. That distribution tells you whether this is a beginner cue or a master-level subtlety.

Pattern statistics

Related concepts

The five concepts most often co-firing alongside this one (Jaccard similarity over the puzzle co-occurrence graph) are:

• Detects a white rook directly contesting a black rook on or near the 8th rank… — similarity 0.034
• A rook is actively placed on a key rank or file where it creates immediate… — similarity 0.022
• Black bishop actively placed in an endgame, often contesting the same diagonal… — similarity 0.012
• An active knight in an endgame tactical position, often delivering or enabling… — similarity 0.009
• A square dominated by a white knight where white has equal or superior control… — similarity 0.005

Example puzzles

Below are 5 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.

• Puzzle zzvln — ELO 1176, themes: crushing, endgame, fork, side to move: White
• Puzzle zzvln_F — ELO 1176, themes: crushing, endgame, fork, side to move: Black
• Puzzle zzvln_M — ELO 1176, themes: crushing, endgame, fork, side to move: White
• Puzzle ztPUy — ELO 1401, themes: crushing, endgame, intermezzo, side to move: White
• Puzzle ztPUy_F — ELO 1401, themes: crushing, endgame, intermezzo, side to move: Black

How to use this page

If you want to train this pattern, open the Climbchess trainer and filter for puzzles tagged with this concept. The trainer surfaces them at the right difficulty for your current rating, and tracks how often you spot the cue versus miss it. You can also browse the related concepts above to see neighbouring ideas in feature space.

Climbchess concepts are not heuristics written by a human author. Each one corresponds to a single direction in the residual stream of Leela Chess Zero that activates on a specific board feature, then was labelled by reading the top-activating positions. This makes the catalogue exhaustive (every Leela-detectable pattern is in here somewhere) and falsifiable (you can replay our extraction).