Hidden Triple
Three heights only fit in the same three cells of a row or column — strip those cells down to just those three.
The solver does not attempt this technique, so Smart Hint will never suggest it. It is documented because you may still want to spot it yourself.
How it works
- 1Track heights 3, 4 and 5 across this row. None of them fits in either of the first two cells.
- 2So all three are confined to the last three cells — three heights, three cells, one each.
- 3Those cells can therefore hold nothing else: strike the stray 1s and the 2.
- 4Notice what this did NOT do: it didn't say which of the three gets the 3. Hidden subsets tidy a line up so the next technique can finish it.
- 5One caveat about the size: in a five-cell line the two cells the triple leaves alone are a Naked Pair on {1, 2}, and that strikes exactly these marks a rung earlier. A Hidden Triple only leads in a line of seven or more blanks — the shape is worth knowing here, but on a board this small something cheaper beats you to it.
- Height ruled out
- Relationship — The arrow shows which cells support the deduction.
- Conclusion — The final arrow lands beside the proved or ruled-out height.