Strong links and three-cell wings

Patterns built on conjugate pairs (strong links) and three-cell wing structures that use bivalue cells to force eliminations.

Skyscraper

Two parallel strong links with endpoints that force an elimination.

2-String Kite

A row and column strong link connected through a box.

Two strong links connect four candidate 2s through a weak link in a Sudoku grid

2 Strong Links

Two conjugate pairs joined by a weak link.

Turbot Fish

A compact single-value forcing chain with the Turbot Fish structure.

An XY-Wing connects a 7 and 9 pivot to two candidate 4 pincers in a Sudoku grid

XYZ-Wing

A three-cell wing with a three-candidate pivot.

Strong links, conjugate pairs and wing logic

For one candidate digit, a strong link exists when a house contains exactly two possible positions: if one is false, the other must be true. Skyscrapers, 2-String Kites, 2 Strong Links and Turbot Fish connect conjugate pairs through cells that see one another. Their shapes differ, but their conclusion is the same: at least one endpoint must contain the digit, so any outside cell that sees both endpoints cannot contain it.

XY-Wing and XYZ-Wing transfer this either-or reasoning to three cells. A pivot links two pincers through carefully matched candidate sets. Whichever value the pivot ultimately takes, a shared elimination candidate is forced in one of the pincers; that candidate can therefore be removed from cells that see every possible source. These guides identify the exact visibility and candidate conditions, which is crucial because a similar-looking arrangement is not automatically a valid wing.

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