1895. The Art of Dressmaking. Figure 10 illustrates another style of shell trimming. This is cut on the bias twice the width it is to be when finished. It generally has an interlining of crinoline, and is then sewed to the skirt in the same manner as shown in the diagram, i.e., to fasten the raw edge up and down. Each shell must be tacked to conceal the adjusting. Length of material required, two and a half times around the skirt, or two and a half yards to make one yard of trimming.