Hello and welcome to the swordfish technique course!

The swordfish technique follows the same principle as the w wing, with the difference of having three basic sets instead of two.

## Examples and practice of the swordfish technique

Let's look closely at the sudoku grid below.

The **6** is the fish figure and the lines R1, R6 and R9 are the base sets.

The candidates for the number **6** in rows R1, R6 and R9 line up perfectly in 3 columns C1, C2 and C9.

There are only two possible options.

Option number one, cells R1-C2, R9-C1 and R6-C9 contain the digit **6**.

Option number two, cells R1-C9, R6-C1 and R9-C2 contain the number **6**.

In any case, these 3 basic sets cover the aligned columns, which means that 6 cannot appear anywhere else in these columns.

So we can confidently remove candidate number 6 for the companion cells.