Indirect Hidden Single

An indirect hidden single also requires candidates to be filled in on the grid first. Then you inspect the candidates within a house (row, column, or box). If one candidate appears only once in that house, then the cell containing it must be filled with that digit.

For example, look at candidate $4$ in row $5$ of the grid below. It appears only once in that row, so $R5C1$ must be $4$. Also, this cannot be seen by cross-hatching alone, because the candidate $4$ in $R5C9$ was actually removed by another technique, namely the naked pair of $\{1,4\}$ in $R1C9$ and $R2C9$.

An indirect hidden single can also appear in a column or a box. For example, in column $3$ of the grid below, candidate $8$ appears only in $R3C3$, so $R3C3$ must be $8$. Likewise, this can only be seen after candidates have been filled in, because the candidate $8$ in $R2C3$ was removed by another technique.

As another example, in box $7$ of the grid below, candidate $2$ appears only once in $R8C2$, so $R8C2$ must be $2$.