Yes, the fishline is taped to the underside of the mask to act as a spacer if you will to keep the mask elevated off the surface. The greater the space the softer the edge.
Again, try new techniques on a test mule first until you are comfortable with the process before trying it on your project.
No one will ever accuse me of taking my modeling secrets to my grave, it is best shared with friends! After all, had no one share theirs with me...I'd be sitting someplace with my fingers glued to a model wondering is this is as good as it gets. It also encourages me to practice and develop more techniques to share!