joint?

 From:  Frenchy Pilou (PILOU) 16 Jun 2009  (1 of 17) 
2691.1 
What are exactly conditions the for make a "Joint"?
Seems very difficult on a sphere!

EDITED: 16 Jun 2009 by PILOU
Attachments:
Attachmentjoint.3dm
Attachmentjoint.jpg