So I want to add exterior fins to my model surface and I use the contour lines to create the curves first. Then I can use the fin tool. But I want these fins to have a thickness so what is the best way to do this so that the fins align with the curved surface they are located on? extrude command? Ideally I would like to create contours which have double lines so that I can then use the fin command from that but not sure how to do that.