What it is
A pointing pair (or triple) appears when every remaining candidate for a digit inside one box lies on a single row or column. The box must place the digit on that line, so the digit can be removed from the rest of the same row or column outside the box.
How to spot it
Work box by box, one digit at a time. When the digit’s candidates inside the box line up on one row or column, follow that line out of the box and eliminate.
Interactive example
Use Next to walk through the deduction on the board.
Step by step
- Find every cell that can hold 4 in the top-left box.
- The middle row of the box is already filled, and the 4 in the third row blocks the box's bottom row.
- All the box's 4-candidates sit in the top row — a pointing pair.
- The box must place its 4 somewhere in that row, so 4 can be removed from the rest of the row outside the box.
Common mistake: Eliminating inside the box instead of outside it. The deduction only restricts the line beyond the box — cells within the box keep their candidates.
Put it into practice
Examples on this page are validated with the Play Sudoku Daily puzzle engine.