GridWits
Expert tier Technique 17 of 46 Reference only

Rectangle Elimination

A near-Unique-Rectangle pattern where a strong link on one corner forces a contradiction if a second corner (the "wing") holds the shared digit — eliminating it there.

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. 1Inside the middle box, digit 3 survives only at E4, D5 and F5 — one cell in column E, two in row 5, nothing anywhere else. That empty corner at E5 is the rectangle the name points at.
  2. 2Row 1 carries a strong link on the same digit: A1 and E1 are its only two homes for 3.
  3. 3If E1 takes the 3, column E loses its others, so E4 goes and the box's 3 has to sit in row 5 — which pushes 3 out of A5.
  4. 4If E1 doesn't, A1 does, and that pushes 3 out of A5 down column A. Either way A5 can't be 3.
  5. 5Deliberately left out of GridWits' ladder: measured against 780 stalled Extreme positions, this shape cracked exactly one that no rung already in the ladder could.

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 3 7 2 3 3 6 3 9 3 8 3 4 3 3 3 3 3 3
  • First colour in the chain
  • Cells that establish the pattern
  • Where the conclusion lands
  • Candidate ruled out
Next in the ladder Remote Pairs →

A connected chain of cells holding the same bivalue pair alternates between its two digits; a target that sees both chain colors can contain neither digit.