Hidden Single

Medium Used by Smart Hint

A digit guaranteed to appear somewhere in this run has only one cell left that can hold it.

Cells that establish the pattern
Where the conclusion lands
Digit ruled out

How it works

The 16-in-two across run must be {7, 9} — and 9 is guaranteed to appear somewhere in it.
But the first cell also belongs to the 7-in-two down run, whose combinations (1+6, 2+5, 3+4) never contain a 9.
The 9 has only one cell left that can hold it — the second one. Place it.