Claiming

If every possible cell for a digit in a row or column lies inside one box, the digit can be removed from the rest of that box.

Level: Elementary · technique 5 of 7

When to use it

It is pointing read the other way round. Pointing starts from a box and clears a line; claiming starts from a line and clears a box.

Look along a row or column with many empty cells for a digit whose candidates all fall inside one box's stretch of it. It is also known as box/line reduction.

How to find it

1. Pick a row or column and a digit it is still missing.
2. Find every cell on the line where that digit can go.
3. Check whether those cells all sit inside one box.
4. If they do, remove the digit from that box's cells that are not on the line.

Worked example

On the board below, look at digit 5 in row 4.

1. Find the cells of row 4 that can take a 5. The other empty cells are blocked by a 5 already in a crossing line or box: r4c2 (the 5 in column 2). That leaves r4c7, r4c9.
2. Those cells all sit inside box 6. So the 5 of box 6 has to be on row 4.
3. No other cell of box 6 can be 5: remove candidate 5 from r6c7, r6c9.

Common mistakes

• Removing on the line itself. The eliminations happen in the box's other rows or columns.
• If it is easy to confuse with pointing, ask where you started: starting from a line makes it claiming.