Intermediate Technique

Pointing Pairs

Use box-line interactions to eliminate candidates when pairs of numbers point to eliminations in other regions.

What are Pointing Pairs?

Pointing Pairs occur when a candidate number appears in only two cells within a 3x3 box, and these cells are aligned in the same row or column. This alignment "points" to eliminations - you can remove that candidate from all other cells in the same row or column outside the box.

This technique leverages the fact that one of the two cells in the box must contain the number, so it cannot appear elsewhere in that row or column.

How Pointing Pairs Work

1

Find restricted candidates in a box

Look for a candidate number that appears in only two cells within a 3x3 box.

2

Check alignment

Verify that these two cells are in the same row or column.

3

Eliminate candidates

Remove the candidate from all other cells in that row or column outside the box.

Example: Row Pointing Pair

In this example, the number 7 can only appear in two cells of the top-left box, and they're in the same row:

Before: Identifying the Pointing Pair

12 46 79
8
123 456 79
123 456 79
5
123 46 79
123 46 789
123 46 789
123 46 789
3
12 456 9
12 456 9
123 46 789
123 46 789
123 46 789
123 46 789
123 46 789
123 46 789
12 456 9
12 456 9
12 456 9
123 46 789
123 46 789
123 46 789
123 46 789
123 46 789
123 46 789

Analysis: In the top-left box, the number 7 (highlighted in green) can only go in two cells, both in the top row. This means 7 must be in one of these cells, so it cannot appear anywhere else in the top row.

Elimination: All 7s in the top row outside the top-left box can be eliminated (shown with strikethrough).

Column Pointing Pair Example

Pointing Pairs also work with columns. Here's an example where candidates in a box point down a column:

Scenario: The number 5 appears in only two cells of a box, and both cells are in the same column. This eliminates 5 from all other cells in that column outside the box.

Key insight: Since one of the two cells in the box must contain 5, no other cell in that column can contain 5.

Step-by-Step Application

  1. Examine each 3x3 box: Look for candidate numbers that appear in exactly two cells
  2. Check alignment: Verify if these two cells are in the same row or column
  3. Identify the line: Note which row or column contains the pointing pair
  4. Find elimination targets: Look for other cells in that row/column outside the box
  5. Eliminate candidates: Remove the candidate number from all target cells
  6. Continue solving: The eliminations may reveal new solving opportunities

⚠️ Common Mistakes

  • Wrong alignment: Make sure the two cells are truly in the same row or column
  • Over-elimination: Only eliminate from cells outside the box, not within it
  • Missing the pair: Check all nine boxes systematically for pointing opportunities
  • Ignoring triples: If three cells in a line within a box contain a candidate, the same elimination principle applies

🎯 Practice Exercise

Look for Pointing Pairs in your next puzzle:

  1. Choose a 3x3 box with several empty cells
  2. For each missing number, identify possible positions within the box
  3. Look for numbers restricted to exactly two cells
  4. Check if these cells align in a row or column
  5. Eliminate the candidate from other cells in that line outside the box

Tip: Pointing Pairs are most effective in boxes that already have several numbers filled in, as this restricts candidate positions.

When to Use Pointing Pairs

  • After basic singles techniques have been exhausted
  • When you have boxes with multiple filled cells
  • As a candidate elimination step before looking for pairs or other patterns
  • When you notice candidates clustered in lines within boxes

Related Techniques

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