X-Wing

Expert

X-Wing is a pattern of one digit across two rows and two columns. It’s the best-known Expert technique, and the first of the “fish”: Swordfish and Jellyfish are bigger versions of it.

How it works

Find a digit that fits in exactly two places in each of two rows, with those places in the same two columns: four cells at the corners of a rectangle. Each row needs its digit, and the two can’t share a column, so they sit on opposite corners. Either way, both columns get their copy from these corners, so no other cell in those columns can hold the digit.

It works just as well turned on its side: two columns whose places line up in two rows clear the digit from the rest of those rows.

How to spot it

• Pick a digit and look for rows (or columns) where it has exactly two notes. If two of them use the same two columns, you have an X-Wing.
• Looking at one digit’s notes at a time, as the picture does, makes the rectangle jump out.
• An X-Wing only helps if the columns have the digit somewhere else to remove: check before you celebrate.

Bigger fish

With three rows whose places fit into three columns, it’s a Swordfish; with four, a Jellyfish.