Hello,
I have a question about the following picture.

From time to time I like to open up exisiting fonts
in Type Tool to see how they work. I recentley opened up
Helvetica Regular and noticed that on the C they have
these guidelines, in Tpye Tool it is located on the Vector
control layer, that follow the curve. When I erase the
guidlines it then erases the section of the font.
What are these lines for and how do you use them?
Thanks!

j o s e p h