So I've been following this blender tutorial and have just created a head using Dyntopo. I am now learning how to finish it with retopo. I started out by turning on snap during transform (snap element: edges, snap target: active), and positioned a small plane the head. The tutorial then went on to explain how to "extrude a poly ribbon" by selecting an edge of the plane and extruding it by pressing control and clicking, as shown below:
When I try to do this, however, it does not seem to work. It just outlines the head in orange, as shown:
What should I try doing differently to make this work for me? If it matters, I am using a mac.