Hidden triple
Three digits fit in only the same three cells of a unit.
A technique for Hard puzzles. Play a Hard puzzle
What it does
Like a hidden pair, with three digits. If three digits can only go in the same three cells of a row, column or box, those cells hold those digits, whatever else their notes say.
How to spot it
In a unit, check where each digit can still go. When three digits are each limited to the same three cells (not every digit needs all three), you have a hidden triple. Other candidates in those cells hide it, hence the name.
What it lets you do
You remove every other candidate from the three cells, leaving only the three digits. That often reveals a pair or a single nearby.
Try it
Find the Hidden triple on this board. Pick the cells it clears, mark the candidates it removes, then check.
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.