Edit
the fur description (either in the Channel Box or Attribute
Editor).
Make
sure the fur has an Inclination value greater than 0.
Right-click
the Polar field, and select Create
New Texture. The Create Render Node window
appears.
Click
the Ramp button.
In
the Ramp Attributes section change Interpolation to None.
Modify
the ramp so that one side of the part has a value of 0.5 (gray)
and the other has a value of 1.0 (white), as in the following illustration.
Position the part where you want it. (In this example, the part
is in the middle of the surface.)