Usage of '' to mean "ditto"

The NOAD reports that '' (two single quotation marks) is a symbol used to mean ditto.

When is it used? Should it be used to replace the same word that appears in the same position but in the previous line?

I always thought it could be a dog.
I then discovered it is all but a ''.


Solution 1:

The ditto mark is a typographic symbol that should be confined to lists, and works best when a non-proportional or monospaced font is used, else it may not appear in the right place.