This one would be useful for drawing details. For instance if you are detailing an inlet and you only want to draw the interior or exterior lines with out offsetting the lines this may work well.
Now that you have created the style we need to apply it to the AECPOLYGON that was just created if you are still in the command type P for Properties, it will ask you to select the AECPOLYGON and select the one you want to change. In the properties window change the style to the one you created. You should end up with a two lines going all the way around which is easier to change then two parallel polylines.