Pointing Pairs: Your First Intermediate Sudoku Technique
Look at a single 3×3 box and pick a digit it still needs — say 3. Pencil in where the 3 could go inside that box, and suppose the only two candidate cells both sit along the top row of the box. You do not yet know which of the two holds the 3, but it is one of them, and both are in that row. So the 3 cannot appear anywhere else along that row — including the two neighbouring boxes the row passes through. Erase 3 from every other cell in that row.
That deduction is a pointing pair, and it is the first technique that feels like real Sudoku logic rather than scanning. You are not solving a cell; you are using a constraint inside one box to clear candidates far outside it, which then sets up the naked and hidden singles that actually fill cells.
What a pointing pair is
When the only candidates for a digit in a box line up in a single row or column, they "point" along that line. Because the digit must occupy one of those cells, it can be eliminated from that whole row or column outside the box. Two candidate cells make a pointing pair; three make a pointing triple, but the logic is identical.
A worked example
Suppose the top-left box can only place its 5 in the two cells of its middle row. Look along that middle row as it continues through the top-middle and top-right boxes. Any 5 penciled into those outside cells can be erased, because the 5 for this row is already claimed by the top-left box. Often that single erasure leaves a cell in the top-right box with just one candidate — a naked single you could not see a moment earlier.
The mirror: box/line reduction
Box/line reduction runs the same logic in reverse. If the only candidates for a digit within a row all fall inside one box, then the digit must sit in that box on that line — so you can erase it from the rest of the box.
The two work as a pincer: pointing pairs clear a line using a box, and box/line reduction clears a box using a line. Together they thin the candidate grid enough for singles to reappear.
Why it matters
Pointing pairs rarely place a digit by themselves. Their job is to remove candidates so that a naked or hidden single becomes visible. That is the rhythm of intermediate Sudoku: an elimination technique opens a gap, and a placement technique fills it. Learn to alternate, and most "hard" puzzles come apart without any guessing.
Do not confuse it with a naked pair
A pointing pair is about a digit confined to a line within a box. A naked pair is something different: two cells in the same unit that share the same two candidates, which lets you remove those two digits from every other cell in that unit. They are separate tools that often turn up together — an elimination from one frequently exposes the other. In practice you scan for both at once: any digit pinned to a single line inside a box, and any two cells locked to the same pair of numbers.
You need pencil marks for this
You cannot spot a pointing pair without candidate marks — the whole technique is about reading where a digit can and cannot go. Turn on pencil marks, keep them accurate, and scan box by box for a digit pinned to a single row or column. In Sukuro the levels above the beginner band make this scanning the main event, and the Hint button will point out a pointing pair and the line it clears when you ask.
Practice it now
On your next medium puzzle, when scanning for singles stalls, switch modes: go box by box and look for any digit whose candidates share a row or column. Clear the line, then re-scan for singles. That one extra habit is usually the difference between finishing a medium board and giving up on it.