GridWits
Extreme tier Technique 31 of 46 Used by Smart Hint

Finned X-Wing

An almost X-Wing with an extra fin candidate confined to one box — eliminations survive where the cover line crosses that fin's box.

How it works

  1. 1Digit 4's homes in row 1 are B1 and E1. In row 2 they are B2 and E2 — and one more, F2.
  2. 2Without F2 those two rows would be a plain X-Wing on columns B and E. F2 is the fin, and it sits in the same box as E1 and E2.
  3. 3If the fin is the 4, that box's other cells lose it. If it isn't, the X-Wing holds and columns B and E lose their 4s outside the two base rows.
  4. 4E3 is caught either way: it lies in cover column E, outside both base rows, and inside the fin's box. Its 4 goes.
  5. 5The coloured fin and the four fish corners should be read separately: only targets that lie in both the fin's box and a cover column can be removed.
  6. 6Sashimi Finned X-Wings use the same either-fin-or-fish proof with a base corner absent.

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 4 7 4 6 4 5 3 4 4 8 4 9 4 4 4 4 4 4
  • First colour in the chain
  • Cells that establish the pattern
  • Where the conclusion lands
  • Candidate ruled out
Next in the ladder Finned Swordfish →

An almost Swordfish whose extra fin candidates are confined to one box — eliminations survive only where a cover line crosses that box.