Hi @hozz__
Edit: I saw your last post after I responded... I don't really know how Inventor is applying the appearances, maybe there is some rhyme or reason to it... but I've never looked at it close enough to know..
I'm not sure what you're looking for?
I showed you the manual way to adjust the face based on the information you provided in your first post, and then you mentioned "This doesn't work when applying appearance programmatically, because the my code doesn't know which of the 2 parts is 90 degrees out to start with"...
The short answer is that Inventor's method of applying appearances is not "smart" and is simply not looking at the the face orientation, or whatever might be used to make the appearance applied in a more accurate manner.
You might be able to find something in the API that would allow you to use the some property of the face to determine the adjustment that needs to be made, but since you state this is not a programming related question then maybe not?
I think that's the best I can do to help, unless you provide a more clear and detailed explanation of what you are asking.
I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com