Techniques › Claiming
Claiming
A digit confined to one box inside a line clears that digit from the rest of the box.
Claiming is Pointing run backwards. Take a row and a digit: if every cell where that digit could still go lies within a single box, the digit must be in that box, so it can be cleared from the box's other six cells.
The two are often taught as one technique — locked candidates — because they are the same observation about a box-line intersection viewed from either side. Worth knowing as two, because you hunt for them differently: Pointing you find scanning boxes, Claiming you find scanning lines.
A worked example
Taken from a real puzzle in our bank, at the point where this was the cheapest move available. Pattern candidates are marked in amber; anything the step eliminates is struck through in red.
| 6 | 2 | 7 | 3 | 1 | 9 | 5 | 8 | 4 |
| 58 | 1 | 3 | 4 | 58 | 2 | 6 | 9 | 7 |
| 9 | 45 | 48 | 7 | 6 | 58 | 1 | 2 | 3 |
| 2 | 45 | 1 | 6 | 9 | 458 | 7 | 3 | 58 |
| 3 | 7 | 48 | 1 | 58 | 458 | 9 | 6 | 2 |
| 58 | 9 | 6 | 2 | 7 | 3 | 4 | 1 | 58 |
| 7 | 3 | 5 | 9 | 2 | 1 | 8 | 4 | 6 |
| 4 | 8 | 9 | 5 | 3 | 6 | 2 | 7 | 1 |
| 1 | 6 | 2 | 8 | 4 | 7 | 3 | 5 | 9 |
- NudgeDigit 5 is pinned to one line inside a box, which rules it out further along that line.
- WhereClaiming in row 5, box 5: r5c5, r5c6
- Do itRemove r4c6 ≠ 5
How to spot it
For each row and column, take each unplaced digit and check whether its remaining cells all fall inside one box.
Where you will meet it
Claiming sits at tier 1 of our ladder, which means it first becomes necessary at Easy. Puzzles below that band never require it, though it may still appear as a shortcut.
Read next
- Pointing A digit confined to one line inside a box clears that digit from the rest of the line.
- Hidden Pair Two digits that can only go in the same two cells own them, whatever else those cells show.