In this series of tutorials about formatting lines in PowerPoint 2011, you have already seen how to apply weight, dash styles, arrowheads, and also gradients to the shape outlines and lines. While all shapes by default do have an outline, you can remove any outline so that you end up with a shape with just a fill, and no outline. Of course, you can also remove the fill of the shape as well — but do remember that a shape with no fill and no outline is as good as invisible!
Learn how to remove the outline from a shape in PowerPoint 2011 for Mac.

