John,
I don't mean the S/E window, I mean the 3D window.
Of course in section they clean-up if they have the same material.
Woody,it's not the same problem.
If I make a row of several instances of this molding object, end to end,
and then assign every other instance a different material,
then, in the 3D window, I can see the joint lines between them.
It is as if the 3D window is behaving like the S/E window but
not completely, if set an instance of the molding object exactly
at the edge of a slab, with both having the same material,
they do not clean-up with each other, as has always been the case
with objects and tool elements.
I'm going to experiment with some Archicad library objects
to see if I can duplicate this behavior.
Thanks for posting back,
Peter Devlin