Start with the idea
Start with one number, one row, and one column. In this example, the number is 7. The row and column links force one far end to be 7, so a cell that sees both far ends cannot also be 7.
Look for this pattern
Look for linked two-choice spots for one number. The links create a pattern you can follow around the board.
This empty board keeps the puzzle numbers out of the way so the pattern is easier to see.
Example
5
3
7
6
7
1
9
5
7
9
8
6
8
6
3
4
8
3
7
2
6
6
7
2
8
1
7
9
4
1
9
5
8
Look here firstFocus on the number 7. One two-choice row and one two-choice column meet through the same 3x3 box.
This technique reviews candidates instead of solving a square right away.
One of the far ends must be 7, so the cell that can see both far ends cannot keep 7.
- Choose one number.
- Connect a two-choice row to a two-choice column through one box.
- Remove that number from the cell that sees both far ends.
first colorsecond colornotes to remove
When to look for it
Use it when one digit has exactly two possible spots in a row and exactly two possible spots in a column, with the links meeting in one box.
How to use it
- Find a row with two notes for one digit.
- Find a column with two notes for the same digit.
- Use the box connection to identify the two far ends, then remove the digit from the cell that touches both far ends.
Common mistakes
- The row and column links must be for the same digit.
- Only remove the note from a cell that touches both far ends.