This routine from Alan Thompson will draw the outline of an LW polyline that has a width. It works with linear and closed polylines, with or without arcs. Start by loading the LISP file, then run the command OPL. The routine includes code to filter out everything except LW polylines with a constant width greater than zero. This means you don't have to be too careful in your entity selection, after which you can choose whether or not to keep the original polyline. The outline polyline(s) are drawn on the same layer as the original. Closed polylines with crossing segments may yield unexpected results.