A square on the 3rd or 6th rank that is not attacked by the opponent, and is either empty or occupied by an opponent's pawn.

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

SAE concept sae_29423 fires when a square on the 3rd or 6th rank that is not attacked by the opponent, and is either empty or occupied by an opponent's pawn.. It appears in 2 of 9,950 Climbchess puzzles (0.0%), spanning ELO 1970–1970 (median 1970).

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This page documents A square on the 3rd or 6th rank that is not…, 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:

A square on the 3rd or 6th rank that is not attacked by the opponent, and is either empty or occupied by an opponent's pawn.

This pattern fires in 2 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 1970 to 1970, with a median rating of 1970. 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:

• A square where white holds a local attacking advantage — fork target, hanging… — similarity 0.222
• [polysemantic — fires on multiple unrelated patterns; needs split] — similarity 0.143
• This feature detects squares that are attacked by White and either undefended… — similarity 0.009
• Black bishop actively placed in an endgame, often contesting the same diagonal… — similarity 0.006
• Pawn on the 7th rank (any file) that is advanced or contested, often with… — similarity 0.005

Example puzzles

Below are 2 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.

• Puzzle zwwhE — ELO 1970, themes: crushing, endgame, fork, side to move: Black
• Puzzle zwwhE_F — ELO 1970, themes: crushing, endgame, fork, side to move: White

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).