Skyscraper Pattern
advancedTwo conjugate pairs sharing one endpoint to form a turbot fish elimination
The Skyscraper is a single-digit pattern that uses two rows (or columns) where the candidate appears exactly twice. When one column is shared, the unshared endpoints create an inference that allows eliminations.
Understanding the Concept
Find two rows where a candidate appears in exactly two cells each.
One column must be shared between the two rows — this is the "base" of the skyscraper.
The other two positions are in different columns — these are the "tops" of the skyscraper.
Logic: In each row, the digit is in one of two cells. The shared column links the rows — if the base cell in row A is true, the base cell in row B is false (same column), forcing the top of row B.
Conversely, the top of row A could be true.
Either way, at least one "top" holds the candidate. Any cell seeing BOTH tops cannot hold the candidate.
This is a turbot fish pattern — a short coloring chain on one digit.
Examples
Skyscraper on Digit 3 (Rows 1 and 6)
Digit 3 in row 1 appears at C2 and C7. Digit 3 in row 6 appears at C2 and C5. Column 2 is the shared base. The tops: R1C7 and R6C5. Cell R6C7 sees both tops (same row as R6C5, same column as R1C7). Eliminate 3 from R6C7. Cell R1C5 also sees both tops — eliminate 3 from R1C5 too.
Pro Tips
- •Scan for a digit that appears exactly twice in two different rows (or columns)
- •Check if those rows share one column — that is the skyscraper base
- •Eliminations target cells that see both "tops" (the non-shared endpoints)
- •Skyscrapers are actually easier to spot than X-Wings once you know the pattern
- •This is equivalent to a short simple coloring chain of length 4
