Pointing Pairs Explained Simply: Find and Apply the Pattern

What is a Pointing Pair?

In Sudoku, a pointing pair is a subset of locked candidates where all possible cells for a given digit within one 3x3 box lie on the same row or the same column. This 'locks' the digit to that line inside the box. The pattern can involve two cells (a pair) or sometimes three cells (a pointing triple). For example, imagine a box where the only places you can pencil in the digit 7 are the top-left, top-middle, and top-right cells. All three are in the box's top row. This is a pointing triple, but the logic for elimination is identical to a pair. Recognizing this pattern is a key step in moving past basic techniques like singles and What to Do When Stuck.

The core principle is simple: because the digit must go somewhere in that box, and all its possible spots are on one line, the digit ultimately must be placed on that line. Therefore, you can rule it out from any other cells on that same line that fall outside the box in question.

How to Scan for Pointing Pairs

The most systematic way to find pointing pairs is to examine each 3x3 box individually, one candidate digit at a time. For the digit you are checking, look at all nine cells in the box. Ignore cells that already contain a number or are blocked by the digit's presence in the corresponding row or column. Ask yourself a key question: Are the remaining possible cells for this digit all located in the same row? Or are they all in the same column?

If the answer is yes, you have found a pointing pair (or triple). This scan works best when you use pencil marks. Without noting all possible candidates, these patterns are much harder to spot. Our hint engine finds that most players miss pointing pairs because they try to visualize all possibilities mentally instead of systematically marking them.

• Scan box by box, not row by row.
• Work digit by digit (1 through 9) within each box.
• Use pencil marks. This technique is nearly impossible to do consistently by sight alone.

What to Eliminate (And What Not To)

Once you identify a pointing pair, you can perform eliminations. The rule is clear: you may eliminate the candidate digit from any cell on the same row or column that is outside the box where the pointing pair is located. The logic is that the digit is guaranteed to be placed somewhere on that line but within the confines of its home box. It cannot appear elsewhere on the extended line.

A critical warning: you must not eliminate the digit from other cells inside the same box. The pointing pair pattern only tells you the digit is on a specific line within the box. It does not tell you exactly which of the two or three cells it occupies. You still need other techniques, like Naked Pairs or singles, to resolve the final placement within those cells. The eliminations you make outside the box often create new singles or other patterns to help with that.

Verification Checklist Before Eliminating

Before you confidently erase any candidates, run through this quick mental checklist to avoid common mistakes. First, confirm the digit is not already placed in the box, row, or column. Second, verify that every possible cell for the digit in the box is indeed on the same row or the same column. Third, double-check that the cells you plan to eliminate from are on the correct line but are outside the box containing the pointing pair.

This verification takes seconds but prevents errors. Many solvers jump to eliminations after seeing two cells in a line, forgetting to check if the digit could also go in a third cell in the box on a different line. For a deeper look at variations, see our guide on Pointing Pairs and Triples.

When Pointing Pairs Are Not Enough

Pointing pairs are an intermediate technique. They are powerful but will not solve every puzzle. Often, applying them will reveal new singles or create other pointing pairs. However, if you are still stuck after finding all pointing pairs, the puzzle likely requires more advanced strategies. The next logical step is often to look for the complementary pattern to pointing pairs.

What if a digit in a row or column is confined to a single box? That is the opposite pattern, called a claiming pair (or box-line reduction from the line's perspective), and it eliminates candidates within that box instead. Beyond that, techniques like Naked Pairs, hidden pairs, and X-Wing come into play. Remember, Box-Line Reduction is the umbrella term that includes both pointing pairs (locked in a box, points to a line) and claiming pairs (locked in a line, claims a box). Mastering both sides of this interaction is crucial for harder puzzles.