1. Create two objects on the sample plane: lines, polylines, ellipses, or elliptical
   arcs.
2. Extrude the objects to create surfaces that are associated with each profile object.
3. Click Parametric tab Geometric panel Parallel. Find
4. Select two profile objects to constrain them to remain parallel to each other. Be
   careful not to select a surface or edge subobject.

If the profile objects are not already parallel, they are moved into a parallel position,
and the parallel constraint symbol is displayed. The associated surfaces also remain
parallel.

Learning AutoCad