The density of the fill can be adjusted so that each line of stitching moves farther apart from the previous line, which makes for a varying density, called a “Gradient.” Gradients are an effect, and not used to provide coverage as a regular fill might. When making a gradient, you have two densities; the starting density, which is the one set for the fill, and the final density, which is the one set in the Gradient property. The gradient can have different styles selected using the list box. Note that a standard fill has a gradient set to “None.”