Mirrored from Sudopedia, the Free Sudoku Reference Guide

# Finned Fish

Finned Fish is a variety of fish that has extra candidates in a single box. Like regular fish, it is a single-digit solving technique.

The same names are used for the different sizes:

Finned X-Wing
Size 2
Finned Swordfish
Size 3
Finned Jellyfish
Size 4

## How it works

Here is an example of a Finned X-Wing:

 . . . / X / . . .
 . . . / X / . . .
 . . . / / / . . .
 . * . F X . . * .
 . . . / X / . . .
 . . . / / / . . .
 . . . . . . . . .
 . . . . . . . . .
 . . . . . . . . .

The four cells marked X would be an X-Wing if the candidate in the cell marked F were not present. So either there is an X-Wing, or the candidate in F is true. In both cases, the starred cells cannot contain a candidate for this digit. We can eliminate those candidates.

The eliminated candidates can only be within the box containing the fin.

The F cell is known as the fin. In this example, there could also be a candidate in r5c3. This would be called a big fin, but the effects are the same.