Expert technique · Technique Academy

Skyscraper

A Skyscraper is a digit with exactly two possible cells in each of two rows, where one cell from each row shares a column. The shared pair forms the base, and the two remaining cells are the roofs.

Professor Cryptic, the owl who teaches in the app
Professor Cryptic is thinking

The reasoning

Why does the Skyscraper work?

The base cells share a column, so they cannot both hold the digit, which means at least one roof does. Any cell that sees both roofs must therefore lose that digit.

A worked example

What does the Skyscraper look like on a real board?

Skyscraper worked exampleA sudoku board with pencil marks. The Skyscraper uses R3C1, R3C4, R5C4, R5C3 and digit 1 (rows 3 and 5). The move strikes candidate 1 in R4C1.516241816839748329715616791653842168167341892529181875463354962781746539218182571846399318168216574
The move strikes candidate 1 in R4C1. Digit 1, rows 3 and 5.
  • Cells that form the pattern
  • Cells that lose a candidate
  • Struck digit: ruled out

Make it stick

How can you practise the Skyscraper?

The Technique Academy in Cryptic gives every technique its own lesson and 5 practice boards that need exactly this move.

Get it onGoogle PlayPlay Cryptic on the web

Further reading: HoDoKu's page on this family of techniques.

EasierHidden QuadHarder2-String Kite