Hidden Triple
Intermediate Removes candidates Used in: Sudoku, Killer Sudoku, Calcudoku, Futoshiki
Three digits are confined to the same three cells of a unit, even though those cells also carry other pencil marks. Lock the three digits into the three cells and clear every other candidate from them.
How to spot it
Three digits that can only go in the same three cells of a unit.
What you can conclude
Clear all other candidates from those three cells.
Worked example
If 2, 5 and 8 only fit three cells of a unit, strip every other pencil mark from those three — they hold 2, 5 and 8 between them.