This layer is the "Hidden Items" layer. It is called ".BLACK_HOLE" and these sketched curves you refer to are automatically placed on that layer when they are used in the definition of a later feature. So this is very normal behavior.
Paul J. Crane Business Analyst - Product Design Computer Aided Engineering Services Deere & Company Worldwide Headquarters - EOB 5-9N One John Deere Place, Moline, IL 61265
