Pointing Pairs

Pointing Pairs (also called Locked Candidates Type 1 or Intersection Removal) is the first technique that uses the overlap between a box and a line. It doesn't place a digit - it clears candidates - but those eliminations are often what unlocks the next single. It's the natural step up once naked and hidden pairs feel comfortable.

What is a Pointing Pair?

Every 3×3 box shares its three rows and three columns with the rest of the grid. Suppose a digit - say 5 - can only go in one row of a box. Then, wherever the 5 ends up in that box, it's on that row. So the 5 can't appear anywhere else on the row outside the box - and you can delete it from those cells.

The candidates "point" out of the box along the line. Two cells make a pointing pair; three make a pointing triple, but the logic is identical.

Step by step

Fill in your pencil marks. Like every intersection technique, this is invisible without a full candidate list.
Pick a box and a digit. Find where that digit can still go in the box.
Check if they share a line. If all of them sit on one row (or one column), you have a pointing pair.
Clear the line. Delete that digit from the rest of the row (or column) outside the box.
Re-scan. The eliminations frequently expose a hidden single on that line.

In the left box the 5 can only go in the top row (indigo). So the 5 is eliminated from the rest of that row - the red cells can no longer be 5.

Pointing pairs vs box/line reduction

These two are a matched set. A pointing pair works from the box outward - a digit locked to a line inside a box clears that line. Its mirror, box/line reduction, works from the line inward - a digit locked to a box inside a line clears that box. Learn them together; between them they crack most intermediate grids.

Common mistakes

Clearing the box instead of the line. A pointing pair eliminates along the line, outside the box - the box cells keep the candidate.
Needing all three cells. Two candidates on the same line is enough; you don't need the digit in all three cells of the box's row.
Missing the column version. The same logic works when the digit is locked to one column of a box - scan both.

Which Sudoku types is this best for?

The same logic applies across variants, but it pays off more in some than others.

Great fit Classic Sudoku One of the two workhorse intersection techniques on any Classic grid. → Great fit Killer Sudoku Cage sums restrict candidates to a line inside a box surprisingly often. → Great fit Sudoku X Works normally; the diagonals add lines a candidate can be locked to. → Great fit Samurai Sudoku Applies per grid, and the shared boxes are prime spots for a locked candidate. →

Where to practise this

This technique starts paying off at Easy, which is where puzzles first stop yielding to anything simpler. Reading about a pattern and spotting it on a live grid are different skills - the second one only comes from playing.

Play Easy Sudoku About Easy Sudoku

Related techniques

Naked Pair - Sudoku Elimination Technique Two cells in a unit holding the same two candidates claim those digits, removing them elsewhere in the unit. Box/Line Reduction in Sudoku (Claiming) A candidate confined to one box within a row or column is removed from the rest of that box. Cage/Unit Overlap - Killer Sudoku Technique Where a cage overlaps a unit, a candidate confined to the overlap is removed from the rest of the cage or the rest of the unit - a candidate, not a sum, technique. Crosshatching - the First Sudoku Scanning Technique Scan a digit's existing rows and columns through a box to find the single cell in the box where it can still go.