Naked Pair
Two cells in a row or column share the exact same two candidate heights — remove those heights from the rest of the line.
How it works
- 1The first two cells of this row are down to the same two heights, {1, 3}.
- 2Whichever way round they fall, between them they use up the row's 1 and its 3.
- 3So neither height can appear anywhere else in the row. Strike both from the other two cells.
- 4That settles nothing — both are left holding {2, 4} — and it doesn't need to. Eliminations first; the placements come out of what the tidier line says next.
- Height ruled out
- Relationship — The arrow shows which cells support the deduction.
- Conclusion — The final arrow lands beside the proved or ruled-out height.