Are you drawing model lines from the Basics/Modeling tab or detail lines from the Drafting tab of the Design Bar. If you are drawing model lines in a view, such as a floor plan then the model line is going to be at the floor plan Level.
Question: Does the line need to show in a 3D view? if not draw detail lines, they have draw order buttons on their Option bar to control what they display over or under.
Also, detail lines display on/across building components.
Mel Persin, AIA