Solving techniques
Pointing pairs and triples
Pointing pairs connect a box with a row or column. They are among the most useful techniques for Medium puzzles.
A pointing pair (or triple) happens when a digit can go only in two or three cells of a box, and those cells are all in the same row or column. The digit must be in that line inside the box, so it can be removed from the rest of the line.
The logic
A box needs one of each digit. If a digit has only two possible cells in the box and both are in column 9, then the digit sits in column 9 in this box. Column 9 only needs one such digit, so no other cell of column 9 outside the box can hold it.
How to find them
- Look at one box and one digit.
- Find all cells in the box where the digit can go.
- If there are two or three, and they share a row or column, you have a pointing pair or triple.
- Remove the digit from the rest of that row or column.
Common mistakes
- Removing the digit inside the box. Only the cells outside the box are affected.
- Missing that a pointing triple needs all three cells on the same line.
- Mixing it up with box-line reduction, the reverse idea.
Reverse view
The opposite pattern is box-line reduction: a digit in a row or column that falls into one box. Both belong to the same family, sometimes called locked candidates. Next on the ladder are triples. For the full order, see all techniques.
Frequently asked questions
What is a pointing pair?
Two cells in a box that hold the only candidates for a digit and lie on the same row or column.
What about pointing triples?
The same idea with three cells. All three must be on one line.
What is another name for it?
Locked candidates (type 1), or box-line interaction.