How can i fix the "orphan" line that appears in the attached image.
Object 2 in the attached file.

Cheers
-kimmo

Merge, applied to the two edges?

And again to two edges of the other surface...

It comes back after the two surfaces are joined or booleaned :(

I had to re-Sweep the "top" with a blend...

Hi kimmo, yes like Brian writes above the Merge command can be used to fix up split edges like that:
http://moi3d.com/3.0/docs/moi_command_reference10.htm#merge

Select the 2 edges, push the Tab key and type Merge then push Enter.

It's not doing any harm though so it's not necessary to do this, and again like Brian says it will get split up again if you rejoin it to the vertical surface since the vertical surface's edges don't line up with its edges:



- Michael