GridWits
Extreme tier Technique 24 of 46 Reference only

Extended Unique Rectangles

A Unique Rectangle's "deadly pattern" idea stretched across three rows, columns, and boxes instead of two, built around a locked triple of candidates.

The solver does not attempt this technique, so Smart Hint will never suggest it. It is documented because you may still want to spot it yourself.

How it works

  1. 1Six cells — columns B and E across rows 1, 2 and 3 — sit inside one band and touch exactly two boxes. That is the shape a Unique Rectangle stretches into.
  2. 2Five of them hold nothing but {1, 2, 3}. If E3 were the same, those three digits would fill all six cells, and they could be rotated around the block to give the puzzle a second solution.
  3. 3A proper Sudoku has one solution, so E3 has to use its extra candidate — strike 1, 2 and 3 and leave the 7.
  4. 4Reference only; GridWits' ladder doesn't carry this one.

Play a Sudoku that needs this technique →

A 1 B 2 C 3 D 4 E 5 F 6 G 7 H 8 I 9 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 7 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
  • Cells that establish the pattern
  • Where the conclusion lands
  • Candidate ruled out
Next in the ladder Hidden Unique Rectangles →

A Unique Rectangle deadly pattern hidden behind extra candidates, uncovered via strong links on one of the pattern's two digits instead of bare bivalue corners.