How to set curve point that will determine the extrusion line

 From:  Metin Seven (SEVENSHEAVEN)
6327.1 
Hi guys,

I'd love to know how I can determine what closed curve point will be the visible line when the curve is extruded. I assume that the visible line on the side of an extruded curve is the edge where the side surface of the extrusion starts and ends?

Thanks!

Metin