Thank you! I believe a group needs to be open for editing in order to use the "intersect faces" command. The extraneous lines, as you indicate, do not result on the group that is being edited. But they still get generated onto tangent groups (which are not open for editing.) Sounds like I need to create an umbrella group in order to corral all the likely suspects into one group that can be open when the "intersect faces" command is utilized? Is that correct?

Is there a way to avoid accumulating outlines, from groups, on surfaces of tangent groups ? Often, when I “hide rest of model” to edit a group, I discover these extraneous lines and spend time erasing them. Are they the result of using the command “edit, intersect faces w model”?