Closing a surface

 From:  Schbeurd
@ Michael :

Thanks ! I will carefully examinate this one and the Crane Hook file you posted some time ago. No doubt that this approach can be useful in a lot of circumstances.

@ Frenchy :
> Question : Only some curves of an object can be "exported" as like an object? (seems not)

Obviously, Michael understood your question. Not me ! ;-) Can you further explain (maybe with a few french words...)
By the way, do you sometimes sleep ??? ;-)))