Thanks guys, Michael interesting idea with chamfer and undo, I made chamfer surface using isocurves in my example. Burrman good idea but looks a bit complicated for me, I use Flow very rarely, it seems to me a bit complicated :) Anyway thanks.
I found today another method that is very fast, you have to set CPlain from view and then cut it. Very simple method but you have to go to ortho view and find good angle to cut.

Pilou, did not know about that stuff, just looked at download page, yes you have to uncheck - use our download manager. There was no this thing in the past :)