W-Wing
Two cells with the same two candidates, linked by a strong link on one of them, eliminate the other candidate from any cell that sees both.
When to use it
Use when two cells far apart share the same two candidates and a strong link on one of those digits connects them.
Worked example
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Two cells share the pair {2,7}; a strong link on 7 connects their columns.
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Whichever way the link falls, one of the two cells must be 2, so 2 is removed from any cell that sees both.
Common mistakes
- Using two cells whose candidates are not exactly the same pair.
- Forgetting that the strong link must be on one of the two shared digits.
Frequently asked questions
What is a W-Wing?
Two cells with the same two candidates, joined by a strong link on one digit. The other digit is then eliminated from any cell that sees both cells.