Although Y-Wing and X-Wing have similar names, the methods are different. X-Wing extends to SwordFish and JellyFish, while
Y-Wing brings a nice set of other rules which we will examine in later articles.

Structurally, Y-Wing is comprised of 3 cells, all of which have exactly two candidates.
One of the cells is called a **hinge** and suppose the two candidates in the hinge are **X** and **Y**. The hinge sees the other two cells,
which will contain a new candidate **Z** and exactly one of **X** and **Y**. In other words, the non-hinge cells will have candidates **XZ**
and **YZ** respectively. Once we have this structure of cells, we can eliminate candidates **Z** from other cells.

Let us first clearly illustrate this structure and see how the eliminations occur. The **hinge** cell is **C6** and the non-hinge
cells are **A4** and **C3**. With the notation above - **X=5**, **Y=2** and **Z=7**. Now, let us see why we can eliminate the
candidate **7** from **A2** and **A3**.

If **C6** has a value of **2**, then **C3** is a **7** and there can be no other sevens in the left square.

If **C6** has a value of **5**, then **A4** has a value of **7** and there can be no sevens in **row A**.

We can now specify the elimination rule of Y-Wing. The **Z** candidate can be eliminated from all cells which are
seen by **both non-hinge cells**.

Let us consider a couple of boards which make use of the Y-Wing method.

In the first example , the **hinge** cell is **D3** and the **Z** candidate is **6**, which is present in the non-hinge
cells **I3** and **D6**.
Placing either **5** or **9** in the hinge cell forces one of the non-hinge cells to become **6** and so we can eliminate the highlighted
candidate in **I6**.

Load in Solver

The second example shows that we can have significantly more eliminations, depending on the positions of the hinge cells.
The setup is the same. The **hinge** cell is **C9** and the **Z** candidate is present in both **B8** and **G9**. On this board,
there are more cells with candidate **6**, which are seen by both non-hinge cells, which leads to more eliminations.
The eliminated candidates are highlighted in red.

Load in Solver

Another method which we will examine later is XY-Chains. The reason for mentioning it here
is that a Y-Wing can be represented as an XY-Chain, where both **Z** candidates in the non-hinge cells are the beginning and end of the chain.