I think that coincident planes will not work because it does not fix the location on the plane. So, I want to fix the location by selecting a particular rectangular area of a larger planar surface on each part.
have you tried the profile center mate?
Your information may be a bit vague. From what I gather, you could have a split line on the surface, and you could use the edges of this split surface for alignment to another part that also has a split line uses on one of it's surfaces.
That should work. Thanks.
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