Swordfish
A digit's candidates in three rows sit in only three columns, so the digit goes from the rest of those columns.
How it works on this board
In each base house, 7 is confined to the same number of cover houses
6
1
5
7
2
2
6
1
5
1
3
2
9
6
2
9
1
1
3
7
2
8
4
9
5
9
6
1
2
5
6
1
6
1
1
5
9
3
2
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