p.s. if you ask for help on a forum you also have to accept that, if the question is "banal" (or seemingly banal), who answers you have the doubt that you are a little nabbo and who advises you to read the guide "autocad for dummies".command: trancia
select objects to be cut: found(s) 1
specify initial point of cutting plan or [Oggetto
piano/surface/assez/vis/xy/yz/zx/3punti) <3punti> sSelect a surface:
select solid section to maintain or [mantieni Entrambi i lati]<entrambi>:
command:</entrambi>
by memory, but I might be wrong, I think it is possible to extrude lines and polylinees open from r2007Now I don't know what autocad version extrudes polylines and turns them into surfaces (maybe even from 12 I don't know) but if you have difficulty extruding an arc (i.e. if you do extruding and selecting the arc) maybe it's the autocad version that doesn't support it.
acido io? : Jiggrin:this not to defend tristan (although sometimes it is a little acid)