A black pawn on the 4th rank supported by another black pawn, with no white pawn directly attacking it.

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

SAE concept sae_8329 fires when a black pawn on the 4th rank supported by another black pawn, with no white pawn directly attacking it.. It appears in 6 of 9,950 Climbchess puzzles (0.1%), spanning ELO 679–2665 (median 2665).

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This page documents A black pawn on the 4th rank supported by…, 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 black pawn on the 4th rank supported by another black pawn, with no white pawn directly attacking it.

This pattern fires in 6 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 679 to 2665, with a median rating of 2665. 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 complex pawn-structure tension in king-and-pawn endgames, typically… — similarity 0.138
• A black pawn on the 6th or 7th rank, undefended by other black pieces, and not… — similarity 0.111
• A vulnerable back-rank pawn or king position creates a skewer or deflection… — similarity 0.094
• White rook actively cutting off the black king in a rook endgame, controlling… — similarity 0.083
• King manoeuvring in a pawn endgame, exploiting key squares and opposition to… — similarity 0.043

Example puzzles

Below are 6 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.

• Puzzle zSwQP — ELO 679, themes: crushing, defensiveMove, endgame, side to move: White
• Puzzle zSwQP_F — ELO 679, themes: crushing, defensiveMove, endgame, side to move: Black
• Puzzle zSwQP_M — ELO 679, themes: crushing, defensiveMove, endgame, side to move: White
• Puzzle zubAZ — ELO 2665, themes: crushing, endgame, pawnEndgame, side to move: Black
• Puzzle zubAZ_F — ELO 2665, themes: crushing, endgame, pawnEndgame, side to move: White
• Puzzle zubAZ_M — ELO 2665, themes: crushing, endgame, pawnEndgame, 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).