X-Wing: lock one digit into a rectangle

An X-Wing uses one digit that appears in exactly the same two columns across two rows, or the same two rows across two columns.

Key idea

Each base row must place the digit once, so both cover columns are occupied by the pattern and the digit is impossible elsewhere in those columns.

See the move, step by step

This worked example uses 7 in rows 1 and 4. The notes show the remaining candidates after earlier solving steps.

Step 1 of 4

Look only at candidate 7 and compare rows with exactly two possible positions.

Base rows

Step 2 of 4

Rows 1 and 4 place 7 only in columns 1 and 4, forming four aligned corners.

Base rowsX-Wing corners

Step 3 of 4

Candidate 7 at R7C1 and R8C4 lies in the cover columns but outside the base rows, so both can be removed.

X-WingCandidates to remove

Step 4 of 4

The corners remain unresolved; only the outside candidates disappear.

X-Wing cornersUpdated cover cells

Make one deduction in each position. All pencil marks come from the displayed grid. These are short technique exercises, not full puzzle completions.

Progress lasts while this lesson is open. Start again to reset these three exercises.

0 of 3 correct

Guided

Find an X-Wing for 2. Select a cell outside the four corners where you can remove it.

Select a cell, then check your move. Use arrow keys to explore the board. The selected cell’s candidates are also shown below at a larger size.

Select a cell to inspect its candidates.

Scan one digit at a time. A rectangle is not enough: all candidates in each selected base row must stay inside the same two cover columns.