A pointing pair happens inside a single box. Look at where a digit's candidates sit within that box: if every one of them falls in the same row, or the same column, the digit is "pointing" out of the box along that line. Since the digit must go somewhere inside the box, and every candidate for it sits on one line, that line cannot hold the digit anywhere else, even in the other two boxes it passes through.
Solvers sometimes call this pattern box-to-line reduction, and when three cells line up instead of two it is a pointing triple, but the logic does not change. You are using a box to restrict a row or column, rather than the other way around.
Easy puzzles never need this and most Medium puzzles skip it too. It is usually the first technique beyond singles that a solver learns, because it needs no pencil marks outside the box, just an eye for where one digit's candidates cluster.
What makes a pointing pair worth learning early is how little bookkeeping it takes. You are not comparing two cells against each other or adding up candidate lists across a whole unit; you are asking one question about one digit inside one box, then applying the answer to a line. That single-question shape makes it the fastest of the intermediate patterns to check for.
Worked example
A real puzzle position with one solution. Step through to see a pointing pair clear a digit out of row 9.
How to find a pointing pair
Pick a box and go digit by digit. For each digit 1 to 9, mark every empty cell in the box where it is still a candidate. Most digits will scatter across two or three rows and columns within the box. Occasionally, though, every candidate cell for one digit lines up in a single row or column.
- Two or three cells both count. A pointing pair has two candidate cells in a line; a pointing triple has three. The elimination works the same way either time.
- Check the box has other empty cells too. If a box only has two empty cells total, of course they share a row or column. The technique matters when the box has several empty cells and the digit still only lives in one line of them.
Pointing pair or box-line reduction?
These two techniques are mirror images. A pointing pair starts in a box and eliminates along a row or column: box points to line. Box-line reduction starts in a row or column and eliminates inside a box: line points to box. If you can find one, it is worth checking for the other nearby, since both often show up on the same crowded board.
Common mistakes
- Eliminating inside the box. The whole point is to clear the digit from the rest of the row or column, outside the box. The candidate cells inside the box that formed the pointing pair keep their marks.
- Checking only two of the box's cells. If a third empty cell in the box also carries that digit as a candidate but sits in a different row or column, there is no pointing pair. Confirm every candidate cell for the digit before eliminating anything.
- Confusing this with a naked pair. A pointing pair is about one digit spread across two cells in a box. A naked pair is about two cells that share exactly two candidate digits. They look similar but the elimination targets are different.
Why Hard puzzles are built around it
Pointing pairs are one of the techniques Hard puzzles are built around. With 28 to 32 givens, Hard boards regularly reach a point where no cell has a naked or hidden single, and the fastest way through is a box that points a digit out of a row or column. Extreme Hard puzzles (23 to 27 givens) need it even more.
Because it only needs candidates for one digit inside one box, this is often faster to spot by eye than pairs or triples, even before turning on the Notes button. Once you get used to scanning box by box, digit by digit, it becomes close to automatic.
Hard boards carry 28 to 32 givens, right where pointing pairs start to matter. Scan each box digit by digit.
Frequently asked questions
A pointing pair is when every candidate cell for a digit inside one box falls in a single row or column. That digit can then be removed from the rest of that row or column outside the box.
The same pattern with three candidate cells in the line instead of two. Some books use pointing pair for both cases; others reserve triple for the three-cell version.
Yes. Box-to-line reduction and pointing pair describe the same move: a box restricting a row or column.
No. Only the candidate cells outside the box, along the same row or column, lose the digit. The cells inside the box keep it.
Pointing pairs start in a box and eliminate along a line. Box-line reduction starts along a line and eliminates inside a box. They are opposite directions of the same idea.
Hard puzzles, at 28 to 32 givens, are where this move becomes necessary once singles run out. Some Medium puzzles use it occasionally too.
Many solvers do, because it only takes one pass through nine digits in one box. Checking every box for pointing pairs first, then moving on to naked and hidden pairs, tends to be the quickest order.