The ‘Pointing Pairs’ method is effective when the same candidate number appears twice within a single row or column of a 3×3 block. Basically, this scenario indicates that the number must occupy one of those two cells, allowing you to eliminate this particular candidate number from the other cells in the same row or column outside the block.
Let me walk you through an example to clarify this technique. As shown in the first image, focus on a 3×3 block highlighted with the purple frame, where the bottom row contains two cells with the number 6. Since this number repeats within the row and not elsewhere in the block, this is our ‘Pointing Pairs.’ This allows you to remove all other instances of 6, highlighted with the green frame, from the rest of the row, as shown in the second image.
This ‘Pointing Pairs’ technique can also be used for two candidate numbers in one cell as shown in the third image. Focus on a 3×3 block highlighted with the purple frame, where the middle row contains two cells with the numbers 5 & 6. Since the number 5 repeats within the row and not elsewhere in the block, this is also our ‘Pointing Pairs.’ This allows you to safely remove all other instances of 5, highlighted with the green frame, from the rest of the row, as shown in the fourth image.
Now you know how this method works. As per my experience, this is an advanced method that can be applied to both easy and hard Sudoku puzzles. Download our free printable Sudoku puzzle books and practice more.