Sudoku FlowPointing Pair vs Box/Line Reduction
Pointing pairs and box/line reduction both work where a box meets a row or column. Here is which way each one points, and what it lets you remove.
Updated 2026-10-04
Pointing pair
Look inside one box at one digit. If every cell of the box that can still hold the digit sits in the same row, the digit must go in that row inside this box, so remove it from the rest of the row outside the box. The same works with a column. With three cells it is called a pointing triple.
Box/line reduction
Now start from a row or column. If every cell of the line that can hold the digit lies inside one box, the digit must go in that box on this line, so remove it from the other cells of that box.
The difference at a glance
| Pointing pair | Box/line reduction | |
|---|---|---|
| Starts from | A box | A row or column |
| Condition | The digit's candidates in the box share one row or column | The digit's candidates in the line share one box |
| Removes the digit from | The rest of that row or column | The rest of that box |
| Level in our app | Hard | Hard |
When to use them
Use them when the singles run out. They never place a digit themselves, but each removal can leave a cell or a unit with a new single.
Learn each technique
Practice
Every Find the Mistake puzzle on this site has exactly one wrong digit, and you can play each board right on its page.
