Normally you will define the Item in the CadConnect header as your final product, and CadConnect will create BOM and Routing belonging to this Item.
If you select this parameter, CadConnect will allow you to work with constructions based on lines only, that is no information, Item, BOM or Routing will be created based on the Header if the Item field in the Header is left blank.
If you select this parameter, but do fill in the Item No. field in the Header, CadConnect will create everything from the header as normal.