Orientation relative to part

I need the orientation of a part relative to another part, in my case I have a plot and items on the plot and I need to get an orientation that is the same regardless of the rotation of the plot, so I then can reverse engineer it to get the actual world orientation.

you could have a main part that is directly in the middle (this only works with models use :getboundingbox()) and have that orientation to be 0,0,0

I’m not sure I understand, could you elaborate?

Edit: a part in the middle that always stays the same way?

don’t models have a World Pivot Orientation can’t you just use that?

image
note: it may just be me because im signed up for beta studio

I only have Pivot Offset Position and Orientation

Found a solution (both b and a are CFrames)

a:Inverse()*b (b relative to a)

https://developer.roblox.com/en-us/articles/object-world-space