I don't know if this has always been the case, or, if it is a problem. I'm making a corner brace drawing, consisting of a right triangle with a "flange" along one of the perpendicular sides. So, I made a 2d triangle with a polyline and simple extruded it to the thickness I need. Then, on the top surface I did a 2d rectangle for the flange and simple extruded it to the depth of the flange.
Next step was to use the 3d Boolean Subtract function to trim the flange piect. I did a 2d polyline of the shape I wanted to remove and then extruded it to the depth of the flange. When I did the Subtract, it worked fine except a portion of the original 2d polyline shape remained. I selected this 2d polyline and deleted it and the end product looks OK.
Taking a closer look at my original extruded triangle, it seems to be in two parts: the extrusion and the original polyline.
Is this the way it is supposed to be? Do I need to delete the original polyline shape to work with the extruded solid shape?
I'm making a part to be eventually 3d printed, so don't want lingering polylines to interfere with the printing process.