Gradient meshes or art brushes based on expanded gradients.
In this case, I believe the simplest way is (or was in earlier versions) to:
1) Create a rectangle with the colour at the edge, of suitable height (corresponding to the width of the pole, see below) and arbitrary length,
2) Copy 1) in front of itself,
3) Reduce the heigth of 2) (over the centre of 1)) to a small fraction and give it the colour at the centre,
4) With 1) and 3) selected Object>Blend>Make (smooth, aligned to path),
5) Drag 4) to the New Brush tab in the Bruhes palette/panel (using defaults).
Then you may apply it to any curve, and change its width by changing the Stroke Weight.
sounds like a cool technique but im a little bit confused,could u pls do a demo for me,like the ones i usualy upload with images.
cool method,works more than perfect!!!!