Controlling line thickness

[Jeff Portwine]

I've never tried cartoline, but the way this is normally done (or at least 
how I've always done it and been told to do it) is the other option that 
Jani suggested, and that is using a circle symbol instead of a "line". 
This will plot a string of circles along the path that the line would have 
followed, resulting in a line with the thickness of the circle radius.

-Jeff