- Box 5: 6 fits only in the highlighted cells.
- Row 6: all the highlighted cells lie in it.
- Row 6: so 6 can go nowhere else.
Pointing in sudoku
Pointing happens inside a box. When all the cells of the box that can still take a number lie in one row or one column, the number must end up in that part of the line. It can then be removed from the notes of the line's other cells, outside the box. Two such cells are a Pointing Pair, three a Pointing Triple.
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How to spot it
Go through a box number by number and look at where each one is still noted. If the notes of a number sit in a single row or a single column of the box, follow that line out of the box and remove the number from its other cells.
Why it works
The box needs the number once, and its only places are in that line. So the line gets its copy of the number inside the box, and no cell of the line outside the box can hold it.
On a real puzzle
This is Pointing on its practice puzzle, at the first step that needs it. The game's hint explains the step like this:
Practice it
This Master puzzle calls for Pointing. Fill in the singles first. When no number is obvious any more, look for the pattern, or ask for the hint: each game has one.