what's rolling the inner fenders mean?

[drudis]

Rolling consists of literally rolling a bat along the fender.

First, remove the 12:00 screw (or you'll have a chip in the paint, like the rest of us).
Then grab an old WOODEN baseball bat.
Shove it in between the fender and the tire.
By rolling the bat, it will slip along the fender (less friction) than it will stick and roll along the rubber tire.
Use this to get the bat 45-degrees and actually make the fender edge from an "L" into a "V" (sort'a).