Hello,
I'm trying to cap an extrusion I created with two offset lines and two regular lines, however it won't work.  I guessing that the capping doesn't work because there are two different line types (polyline, linear line) / surfaces when extruded (untrimmed surface, open brep).  I have tried several different methods to extract the lines to make them all the same (including exploding, extracting brep components, flattening the tree) but none have worked.  Can anyone give any advice/help? 

Thanks.