- Row 3: 3 fits only in the highlighted cells.
- Box 2: all the highlighted cells lie in it.
- Box 2: so 3 can go nowhere else.
Claiming in sudoku
Claiming is Pointing seen from the line. When all the cells of a row or column that can still take a number lie inside one box, the line "claims" the number for that box. The number can be removed from the notes of the other cells of the box.
Or scan with your phone
How to spot it
Go along a row or column number by number. If a number is noted only in cells that share one box, look at the rest of that box and remove the number from its notes there. It is easy to miss, because the pattern is in the line and the removal is in the box.
Why it works
The line needs the number once, and its only places are inside that box. So the box gets its copy of the number from that line, and no other cell of the box can hold it.
On a real puzzle
This is Claiming 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 Claiming. 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.