Hidden Triple

A Hidden Pair occurs when three digits are candidates only in three cells of a house. Other candidating digits can be eliminated from these cells.

In the following sudoku diagram in the second row, the digits 1, 6 and 7 can only be placed in the R2C5, R2C6 and R2C9 cells. The remaining digits 3 and 4 can be eliminated from these cells. Thanks to this elimination, the digit 3 in the middle top box can only be placed in the R3C6 cell.