Pointing
When a digit's candidates inside a box sit in one row or column, they can go from the rest of that line.
How it works on this board
Within the box, 5 is confined to one line
8
4
7
6
3
1
2
2
6
5
9
4
7
8
1
3
5
8
2
4
7
6
9
7
3
3
7
6
3
6
5
8
9
9
2
7
1
6
8
9
3
6
7
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