W-Wing

W-Wing uses two bivalue cells with identical candidates {X, Y} that are not peers. A strong link on one of the digits (say X) in a separate unit ties them together: in that unit, X has exactly two candidates, one of which is a peer of cell A and the other a peer of cell B.

If one bivalue is X, the strong link forces the other bivalue to also be X — contradiction. So one of them must be Y, which means Y can be removed from any cell seeing both.

When to look for it

Once you start scanning for chain logic, W-Wings appear among matched bivalues that aren't direct peers.

How to apply it

1. Find two bivalue cells with identical candidates {X, Y}, not peers.
2. Find a unit where X has exactly two candidates, each a peer of one of the bivalue cells.
3. Eliminate Y from cells seeing both bivalue cells.

Example