Quick answer
Rook Endgame Side Checks is an endgame technique: Lucena bridge-building. Work from the first evidence position for Rook Endgame Side Checks, and begin by testing Kc5.
Begin from Kc5 in 6k1/2P4r/2K5/8/8/8/8/5R2 w - - 2 2. Count the material, king routes, promotion squares and reserve tempi before applying a theoretical rule. The evidence answer is: Rook Endgame Side Checks: use the king's shelter and a checking-distance bridge before advancing the pawn. Candidate line: Kc5.
In the Rook Endgame Side Checks example, notice: side White; pieces Black king g8, White pawn c7, Black rook h7, White king c6, White rook f1; legal first moves c8=N, c8=B, c8=R+, c8=Q+, Kb7, Kd6, Kd5, Kc5. Those legal moves describe the current example board; they do not define a permanent rule set.
Material and result question
The first evidence board tests Lucena bridge-building; the second board tests Lucena bridge-building. A opens with the string direct FEN setup, whereas B opens with direct FEN setup. Browse the Chess Wiki together with the Endgames hub for shared terms. Then compare Material Values with Rook Endgame Bridge Building, Active King In Rook Endings, Four Rook Endgame Principles around a reserve pawn move.
The two inventories make the distinction concrete. A contains side White; pieces Black king g8, White pawn c7, Black rook h7, White king c6, White rook f1; legal first moves c8=N, c8=B, c8=R+, c8=Q+, Kb7, Kd6, Kd5, Kc5; B contains side White; pieces White king b7, White pawn c7, Black rook g7, Black king g6, White rook f5; legal first moves Ka8, Kb8, Kc8, Kc6, Kb6, Ka6, Ka7, Rf6+. Compare the side to move before comparing the labels in the context of the side-to-move tempo.
Topic dossier for this page and board pair r1:6k1 | r2:2P4r | r3:2K5 | r4:8 | r5:8 | r6:8 | r7:8 | r8:5R2 / r1:8 | r2:1KP3r1 | r3:6k1 | r4:5R2 | r5:8 | r6:8 | r7:8 | r8:8: start with a reserve pawn move; then test the side-to-move tempo; keep the conversion move order separate from the active rook before the pawn push; use the defender's only active counterplay as the transfer check; and reserve an outside passer used as a decoy for the exception.
Conversion or defense plan
On the first board, calculate Kc5 after Kc5 and write down the opponent's best reply around a reserve pawn move. On the second board, calculate Ka8 after Ka8 and check the side-to-move tempo. Separate the practical conversion question from the result question; side to move and one checking distance can change the conclusion. In this case the useful condition is an outside passer used as a decoy.
Key claim: Rook Endgame Side Checks is illustrated here by Lucena bridge-building; the first concrete test is Kc5. The board anchor is 6k1/2P4r/2K5/8/8/8/8/5R2; the example is intentionally narrower than the topic label and should not be generalised without checking the surrounding position..
Practical boundary: To answer “What exact king, pawn, and move-order conditions decide rook endgame side checks, and how should each side play them?”, compare the recorded setup with Ka8 and the opponent's reply. The decision is useful only when the stated condition survives that concrete test on board 8/1KP3r1/6k1/5R2/8/8/8/8. The evidence records No tablebase outcome is asserted by this generated record; verify the exact FEN before publication and the second board signature r1:8 | r2:1KP3r1 | r3:6k1 | r4:5R2 | r5:8 | r6:8 | r7:8 | r8:8. The false-positive test is whether the conversion move order appears without the active rook before the pawn push, so the conclusion is useful only when the stated condition survives that concrete test.
Evidence positions
example-1: Lucena bridge-building
Show answer
Rook Endgame Side Checks: use the king's shelter and a checking-distance bridge before advancing the pawn. Candidate line: Kc5.
Why this position is here: Rook Endgame Side Checks is represented by Lucena bridge-building. This is a direct FEN setup with board anchor 6k1/2P4r/2K5/8/8/8/8/5R2; no opening history is inferred from the diagram.
FEN: 6k1/2P4r/2K5/8/8/8/8/5R2 w - - 2 2
Question: What is the first concrete decision in this rook endgame side checks position?
Answer cue: Rook Endgame Side Checks: use the king's shelter and a checking-distance bridge before advancing the pawn. Candidate line: Kc5. The first candidate to test is Kc5. Replay Kc5 on board anchor 6k1/2P4r/2K5/8/8/8/8/5R2 and write down what changes after it.
Evidence boundary: No tablebase outcome is asserted by this generated record; verify the exact FEN before publication.
example-2: Lucena bridge-building
Show answer
Rook Endgame Side Checks: use the king's shelter and a checking-distance bridge before advancing the pawn. Candidate line: Ka8.
Why this position is here: Rook Endgame Side Checks is represented by Lucena bridge-building. This is a direct FEN setup with board anchor 8/1KP3r1/6k1/5R2/8/8/8/8; no opening history is inferred from the diagram.
FEN: 8/1KP3r1/6k1/5R2/8/8/8/8 w - - 6 4
Question: What is the first concrete decision in this rook endgame side checks position?
Answer cue: Rook Endgame Side Checks: use the king's shelter and a checking-distance bridge before advancing the pawn. Candidate line: Ka8. The first candidate to test is Ka8. Replay Ka8 on board anchor 8/1KP3r1/6k1/5R2/8/8/8/8 and write down what changes after it.
Evidence boundary: No tablebase outcome is asserted by this generated record; verify the exact FEN before publication.
example-3: Lucena bridge-building
Show answer
Rook Endgame Side Checks: use the king's shelter and a checking-distance bridge before advancing the pawn. Candidate line: Rd8.
Why this position is here: Rook Endgame Side Checks is represented by Lucena bridge-building. This is a direct FEN setup with board anchor 2R5/R6r/5k2/2K5/8/8/8/8; no opening history is inferred from the diagram.
FEN: 2R5/R6r/5k2/2K5/8/8/8/8 w - - 3 4
Question: What is the first concrete decision in this rook endgame side checks position?
Answer cue: Rook Endgame Side Checks: use the king's shelter and a checking-distance bridge before advancing the pawn. Candidate line: Rd8. The first candidate to test is Rd8. Replay Rd8 on board anchor 2R5/R6r/5k2/2K5/8/8/8/8 and write down what changes after it.
Evidence boundary: No tablebase outcome is asserted by this generated record; verify the exact FEN before publication.
Reading the line
Read the first example (id example-1) as a complete record: continuation Kc5, source tablebase. This is a direct FEN setup with board anchor 6k1/2P4r/2K5/8/8/8/8/5R2; no opening history is inferred from the diagram. If A does not expose Lucena bridge-building, correct the evidence before relying on the prose.
Read the second example (id example-2) separately: continuation Ka8, source tablebase. Its feature is Lucena bridge-building; inventory side White; pieces White king b7, White pawn c7, Black rook g7, Black king g6, White rook f5; legal first moves Ka8, Kb8, Kc8, Kc6, Kb6, Ka6, Ka7, Rf6+. Compare what changes between Kc5 and Ka8.
Boundary cases
The main mistake to avoid with Rook Endgame Side Checks is applying a remembered endgame rule while ignoring side to move, king placement or an unverified result. In A, the missing condition must be located in r1:6k1 | r2:2P4r | r3:2K5 | r4:8 | r5:8 | r6:8 | r7:8 | r8:5R2 after Kc5; in B, test it against r1:8 | r2:1KP3r1 | r3:6k1 | r4:5R2 | r5:8 | r6:8 | r7:8 | r8:8 after Ka8.
For Rook Endgame Side Checks, the first board's evidence boundary (after Kc5) is No tablebase outcome is asserted by this generated record; verify the exact FEN before publication. The second board's evidence boundary for Rook Endgame Side Checks is No tablebase outcome is asserted by this generated record; verify the exact FEN before publication. If a trusted source or careful calculation changes the conclusion around the defender's only active counterplay, update both the evidence record and this article.
Practice from a real game
play the position for both sides, record the critical tempo, and verify the exact FEN against the cited tablebase before publication. Start with A's side to move and r1:6k1 | r2:2P4r | r3:2K5 | r4:8 | r5:8 | r6:8 | r7:8 | r8:5R2; record two candidates, the reply to Kc5 and the correction. Repeat with B's side to move and r1:8 | r2:1KP3r1 | r3:6k1 | r4:5R2 | r5:8 | r6:8 | r7:8 | r8:8; the changed board tests transfer rather than diagram memory.
After the drill, compare your notes with Rook Endgame Bridge Building, Active King In Rook Endings, Four Rook Endgame Principles through the active rook before the pawn push. Keep A's rejected alternative beside B's chosen line Ka8; this shows whether the conclusion survived a new board signature.
Sources and scope
Sources for Rook Endgame Side Checks: Syzygy tablebase verification reference, 1chess.online editorial scope. Source ids are tablebase, original-analysis. Primary evidence hook: tablebase. Comparisons and practice notes are editorial. Evidence revision: 2026-08-remediation-r2.
Scope note for board pair r1:6k1 | r2:2P4r | r3:2K5 | r4:8 | r5:8 | r6:8 | r7:8 | r8:5R2 / r1:8 | r2:1KP3r1 | r3:6k1 | r4:5R2 | r5:8 | r6:8 | r7:8 | r8:8: this page does not claim that Kc5 is an engine principal variation, that an exact endgame result is verified when the evidence says it is not, or that a tool output replaces human calculation. The conclusion is limited to the recorded boundary and the exception the conversion move order.