This option allows the element code to be changed for groups of elements in the current polygon, or by reading a polygon file. When a grid is set up, the separate element types should be defined by creating separate polygons in {TOP}DEFINEGROUP and saving all these polygons in a file. Then to set element codes for any modification of this grid, read the polygon file here. The first polygon (ususally the whole polygon) defines element code 1, the second defines code 2, etc.