Hint highlights two tiles that can be matched. If you have already selected one tile, it will show a match for that piece if one exists.

Hint can be accessed by clicking Mahjongg ▸ Hint. Alternatively, use the Hint button in the header bar, or press Ctrl+H.

Hint can make Mahjongg too easy, and should be used sparingly.

There is a 30-second penalty for each use of the "hint" option.

Video demonstration

You can use Hints to help you find identical tiles.
Press Ctrl+H.
There is a 30 s penalty for each use of this option.