Academy
Pointing PairPointing Pair sudoku technique
Look at where a digit can still go inside one 3×3 box. If every remaining spot happens to sit in the same row or the same column, the box has made a promise: the digit will be placed on that line, inside that box. The rest of the line — the six cells running through the neighbouring boxes — can drop the digit entirely.
How to find a pointing pair
- Take a box and a digit not yet placed in it.
- Mark the cells in the box where the digit could go.
- If all of them line up in one row or column, remove the digit from that row or column outside the box.
- Repeat per digit; pointing pairs come in clusters and love to chain into singles.
The pattern on the grid
A real position — every pencil mark computed, every red candidate a verified elimination. Toggle to see the grid after the move.
Locked Candidates (Pointing) on 3 in b8: r9c4, r9c5 => r9c7<>3
534719286896000000127068400482197653315826040769003020200670000600980000908004060
Standard 81-character format (0 = empty) — paste it into your solver of choice and verify the move yourself.
Worked example
Digit 3 in this position has its candidates at r9c4, r9c5 — the box confines the digit to one line. That intersection must receive the 3, so the remaining candidates fall: r9c7<>3. Nothing else about the position matters; the overlap alone carries the argument.
When it fails
The promise only holds while ALL of the digit's spots in the box share the line. One overlooked candidate on another row of the box and the pointing pair evaporates — recheck the box before erasing outside it.