A naked triple is three cells in one house whose candidates, pooled together, come to exactly three digits. The three cells must take those three digits among themselves, so the rest of the house drops all three from its pencil marks.
The subtlety — and the reason triples are harder to spot than pairs — is that no cell needs to show all three digits. Cells holding {4,5}, {1,4,5}, and {1,5} pool to {1,4,5}: three cells, three digits, triple. Scan houses for small-candidate cells whose marks keep drawing from the same short list.
It works by the same counting as the naked pair, one bigger: three cells sharing a pool of three digits soak all three up. If any of those digits sat elsewhere in the house, the three cells would be left with only two digits to share.
On the board
In the left-middle box, three cells lean on the same short list: R4C1 shows {4,5}, R4C3 shows {1,4,5}, and R5C3 shows {1,5}. Pooled, that is exactly three digits — 1, 4, and 5 — across three cells, so the box’s other cells give them up. R5C2 drops the 1 and the 5, keeping {3,8,9}. And R4C2, which held {1,4,5,8}, loses three pencil marks at once: only the 8 survives, turning it into a naked single on the spot.
This is the exact board the app's interactive Naked Triple demo uses — step 19 of its 62-step walkthrough, drawn here with its live pencil marks.
