W-Wing
Advanced Removes candidates Used in: Sudoku, Killer Sudoku
Two cells hold the same pair {A,B} and are joined by a strong link on B (a unit where B fits only two places). One of the pair must be A, so A is removed from any cell that sees both pair cells.
How to spot it
Two cells holding the same pair {A,B}, linked by a strong link on B.
What you can conclude
Eliminate A from any cell that sees both pair cells.
Worked example
Two {2,5} cells linked by a strong 5 link force one of them to 2, so 2 can be removed from any cell that sees both.