Cross-Hatching
Scanning applied to a single box: rule out cells row by row and column by column until one remains.
What it is
Cross-hatching narrows a digit's position inside one box. You look at the three rows crossing the box and strike out those already containing the digit, then do the same with the three columns. The surviving cells are the only candidates, and frequently just one is left. The name comes from the crossing pattern the eliminated lines make.
How to spot it
Pick a box and a digit that is missing from it. Check each of the three rows through the box: does it already contain that digit elsewhere? If so, the whole row is out. Repeat for the three columns. Count what survives.
Worked example
Step through the reasoning below. Each step adds one layer: first the position, then the pattern, then the candidates involved, and finally what can be eliminated.
Step 1 of 3: The starting position
- Pattern cells
- 3/3
- Digits
- 8
- Eliminations
- —
Press a marked square to point it out on the board above.
Why it matters
Cross-hatching is the most systematic way to work a box, and it is the technique that most reliably converts a half-finished grid into placements. Because it is exhaustive within one box, it also tells you clearly when a box has nothing left to give.
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.
Play EasyStuck on a grid of your own?
Type the position into the solver and it walks the whole solution, naming the technique behind every step — including this one.
Open the solverPrefer paper? Ready-made Easy sets as a PDF.Print puzzles
Finished reading? Mark it done and the learning path remembers where you got to.