The Line Style field lets you select from several different styles for the line or lines that comprise the current element. Click the drop-down button and select the style you want the line(s) to use. You may want to try all five of the following options to see which works best for you:

Dash Select this option if you want the line(s) to consist of dashes.
Dash-Dot Select this option if you want the line(s) to consist of alternating dashes and dots.
Dash-Dot-Dot Select this option if you want the line(s) to consist of a repeated pattern of a dash followed by two dots.
Dot Select this option if you want the line(s) to consist solely of dots.
Solid Select this option if you want the line(s) to be solid.