Sudoku techniques · Hard
Pointing Pair in Sudoku
A Pointing Pair is the first technique that removes candidates instead of placing a number. When a number's only two spots inside a box sit in the same row or column, the box must use that line for it, so the number can be erased from the rest of that line outside the box.
Also known as: Locked Candidates Type 1, Box-Line Interaction.
Why it works
If a number in a box can only go on one line, that candidate is removed from the rest of that line outside the box.
How to spot it
This is a box-first scan. Take one number and mark every cell in a box where it could still go.
- If the surviving cells all sit in one row or one column, you have a Pointing Pair, and the line outside the box loses that candidate.
- Nothing gets placed here. The payoff is the Hidden or Naked Single the elimination creates a move later.
- Boxes on the edge of the grid produce these most often, because they have fewer crossing lines to spread the candidate across.
Builds on
Worked examples
These are the app's own lesson boards. Step through them the same way a hint does.
Row Pointing
A candidate in a box is confined to one row.
- 1
In this box, every cell where 5 can still go lies in the same row.
- 2
So we can remove the candidate 5 wherever it appears in that row outside this box.
Column Pointing
A candidate in a box is confined to one column.
- 1
In this box, every cell where 5 can still go lies in the same column.
- 2
So we can remove the candidate 5 wherever it appears in that column outside this box.