Cross-hatching
Work through one box calmly: cross out the rows and columns where the digit already appears.
What it is
Choose one digit and one box where it is missing. Look at the three rows through the box first: if the digit is already in a row, cross out that row’s square in the box. Then do the same with the three columns. If only one square survives, that is the digit’s home. The square can still allow other digits — the crossed lines are what decide it.
How to spot it
Stay inside one box and use a fixed order: rows, then columns. Mark a row or column only when you can see the digit already placed on it. Never guess from pencil marks. When the final available square is obvious, you have finished the cross.
Worked example
One direction at a time: cross out rows first, then columns for the 4.
Step 1 of 4: Look at the highlighted box
The 4 is missing from this box. We will cross out squares systematically.
Why it matters
Cross-hatching turns scanning into a repeatable routine. It prevents your eyes from jumping around and is especially useful whenever a box has several empty squares.
Practise now
Solve a puzzle where this technique decides the game
Frequently asked questions
What is the difference between scanning and cross-hatching?
They are two views of the same idea. Scanning follows a digit across the board; cross-hatching works within one box and tests all three rows and columns systematically.
When does cross-hatching stop working?
When every box has two or more possible cells for each missing digit. That is the point to switch on pencil marks and look for pairs and other subsets.
Put it to use
Where you will meet it
This pattern is the backbone of easy grids. Start one and you will use it within a few moves.
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