Hi, I am trying to create 2 separate parts, they are the front and back half of a complex casting. This way, any changes to either part will be simplier to accept and will not break my entire model, just 1 half of it. Is there any way to fuze, or join the two parts together ( using a derived part?) so that it can be treated as a single part, just as if it was developed that way from the beginning? PS I do not want to use an assembly, it must be a part file. Thanks Stu