An obturator for an opening of predetermined outline produced in a metal sheet comprising a cap, at least one stiff wall projecting transversely of said cap and at least one snap-fastening blade having a resting position in the absence of urging in which it extends in a direction parallel to said cap, said snap-fastening blade being moveable parallel to said cap against elastic return forces returning it towards said resting position, said snap-fastening blade having an insertion cant adapted to bear on the surface of said metal sheet delimiting said opening when the obturator is pushed therein, said insertion cant sloping relative to a direction transverse to said cap such that said snap-fastening blade is driven to displace to pass through said opening and that slope progressively increasing between said attachment end and said free end.