Naked triple
Three cells in a unit hold only three digits between them.
A technique for Hard puzzles. Play a Hard puzzle
What it does
Like a naked pair, with three cells. If three cells of a row, column or box together hold only three different digits, say 2, 5 and 8, they take those three digits between them. No cell needs all three: 2 and 5, 5 and 8, and 2 and 8 still make a triple.
How to spot it
With your notes written in, look in each unit for three cells whose candidates, put together, are only three digits. Cells with two candidates are the usual building blocks.
What it lets you do
You remove those three digits from every other cell of the unit, and of a second unit the three cells share, such as a box.
Try it
Find the Naked triple on this board. Pick the cells it clears, mark the candidates it removes, then check.
These are the notes after the easier steps: some candidates are already removed, as they would be in your game.
Practise it
The best way to learn a technique is to meet it in a real game. Practice puzzles are sure to need it, at Hard level; any Hard puzzle may need it too.