Box Brain Sudoku
Learn › Pointing Pairs
Medium · technique 11 of 18
Pointing Pairs
Within a box, a digit fits only along one row or column (or the other way round). Also called an intersection, locked candidates or box/line reduction.
How it works
Wherever it lands, it is in that line and that box, so remove it from the rest of the line (or box).
A worked example
Intersection: in row 3, 1 is confined to the cells shared with box 1, so 1 is removed from the rest of box 1.
- The area to look at
- The cells that make the pattern
- Candidates it rules out
A real position from a puzzle in the app. Small digits are the candidates the step looks at; coloured digits are already solved.
Practise it in Box Brain Sudoku
The app teaches Pointing Pairs on this same board, then hands you puzzles that need it. When you are stuck mid-game, a hint first points you to the right area, then names the technique and shows the move.