What is a contour drawing?  It is the outside edge of the object.  This line doesn’t really exist,but we perceive it that way.  We use lines in contour drawings to make the image more appealing. They are very useful in separating image from background. How does variation of line thickness affect a drawing? It adds volume to the picture. It can appear to be 3d-like,have weight,can create various distances within the picture. Using too heavy a line can have the opposite affect;looking like a border. What are the three types of lines in regard to composition? Actual line: a solid,and is a mark of some kind that has a beginning and end. Implied line: A car driving down a road;plane coming in to land;a row of trees  along the road,are a few examples. This line is perceived when there’s no real line. Imaginary line:(psychic line or psychic wire) This line is a very useful tool in that it can take you on a journey across an image(s). It will have your eyes following the artists(or designer) intended path. The way things are placed in your design:pictures,type,designs,can make imaginary lines that are very helpful in getting a pleasing to the eye look.