---
title: "Finned X-Wing: Sudoku Technique #30 | Sudoku Flow"
description: "Finned X-Wing: A fin is one extra cell on a base line that stops an X-Wing from being complete, so the candidate can be removed only from cells in the fin's…"
url: https://sudokuflow.com/lessons/finnedXWing/
language: en
---

[Sudoku technique lessons](https://sudokuflow.com/lessons/) / Finned X-Wing

Lesson 30

# Finned X-Wing

## The rule

A fin is one extra cell on a base line that stops an X-Wing from being complete, so the candidate can be removed only from cells in the fin's box, outside the X-Wing corners and the fin, that lie on a crossing line through an X-Wing corner in that box.

## Step by step

1. 5 almost forms an X-Wing in two base rows. The fin is one extra cell in one of those rows that also has 5 as a candidate.
2. This X-Wing sits on two base rows. We can remove the candidate 5 only from cells inside the fin's box that lie outside the X-Wing corners and the fin, and that share a column with an X-Wing corner in that box.

[Read the full lesson, with more examples →](https://sudoku.rubigogames.com/techniques/finned-x-wing.html)

In our app, when this technique is the next step, the hint names it and shows you why, step by step. No ads, free to download.

[App Store iPhone, iPad, Mac](https://apps.apple.com/app/apple-store/id6502922368?pt=125379530&ct=sudokuflow_cta&mt=8) [Google Play Android](https://play.google.com/store/apps/details?id=com.rubigogames.sudoku&referrer=utm_source%3Dsudokuflow%26utm_medium%3Dcta%26utm_campaign%3Dlesson)

## Try it on more boards

Each board is a real puzzle from our app, at a moment where Finned X-Wing applies. Find the step yourself, or tap Hint and the app's own hint walks you through it.

Finned X-Wing practice board:

```text
7* .  .  | .  .  .  | 4  3  .
1* 8* 9  | 4  3* 5  | 7  6* 2
4* 3  .  | .  2  7  | .  8* 9
---------+----------+---------
.  .  4  | 7* 1* .  | 9  5* 3
.  7  .  | 5* .  .  | .  2* .
.  5  .  | 3  .  .  | 8  7* .
---------+----------+---------
2  1  7* | .  .  .  | .  9  .
.  4* 8  | 9* 5  .  | 2  1  7
5* 9* .  | 2* 7  1* | .  4* 8
```
Digits marked * were filled in by a player; the others were printed with the puzzle.

![Sudoku app icon](https://sudokuflow.com/assets/app-icon.png)

## Want more boards like this?

We also make a Sudoku app for iPhone, iPad, Mac and Android. There are no ads in it at all, it works offline, and when you ask for a hint it shows you the technique instead of just filling in a number.

[App Store iPhone, iPad, Mac](https://apps.apple.com/app/apple-store/id6502922368?pt=125379530&ct=sudokuflow_web&mt=8) [Google Play Android](https://play.google.com/store/apps/details?id=com.rubigogames.sudoku&referrer=utm_source%3Dsudokuflow%26utm_medium%3Dweb%26utm_campaign%3Dsite)

Sudoku Flow is made by Rubigo Games, the developer of the Sudoku app recommended on this site.