Unique Loop Type 1
Two digits form a loop that would give two solutions. With the spare candidates in one cell only, that cell is decided.
How it works on this board
Assuming the target lets the highlighted pattern swap into a second solution
2
1
9
5
7
1
2
3
8
7
2
5
1
4
4
9
1
7
1
8
4
8
7
4
3
5
9
8
4
1
2
4
5
3
4
5
6
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