Pointing Pair
A digit confined to one line within a box can be removed from that line outside the box.
What it is
When all candidates for a digit inside a box sit in the same row (or column), the digit must end up on that line somewhere within the box. The line therefore already has its copy of the digit reserved, so every cell on that line outside the box can drop it. Two cells make a pointing pair, three a pointing triple; the logic is identical.
How to spot it
Go box by box. For each missing digit, mark where it could go inside the box. If those cells all share a row or a column, you have a pointing pair. Then look along that line beyond the box and remove the digit from the cells there.
Worked example
One observation at a time: keep the 5 inside its box, then follow its line outward.
Step 1 of 4: Look inside the box
The 5 can only use the two marked squares in this box.
Why it matters
This is one of the highest-value techniques relative to its difficulty. It is quick to check, applies constantly on medium and hard puzzles, and frequently produces the eliminations that create hidden singles elsewhere.
Practise now
Solve a puzzle where this technique decides the game
Frequently asked questions
What is the difference between pointing and claiming?
Pointing goes from box to line: the digit is confined within a box, so you clear the line outside. Claiming goes from line to box: the digit is confined within a line, so you clear the rest of the box.
Does the pattern need exactly two cells?
No. Two or three cells work equally well, as long as they all lie on the same row or column inside the box. Three cells are sometimes called a pointing triple.
How often does this apply?
Very often. On hard puzzles it is usually worth a full box-by-box check whenever you get stuck, before trying anything more complicated.
Put it to use
Where you will meet it
Medium grids are where this move starts to matter: the obvious cells run out and the pattern takes over.
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