Abstract: A method of producing a hollow monobloc body in a mold which includes the steps of separating the shells of the mold from each other, interposing an element attached to a support between the shells, forming a parison between the shells and around the element, bringing the shells together to enclose the parison and the element, and producing by blowing a hollow monobloc body having an orifice therein which surrounds the element and has its interior wall spaced therefrom. The body is removed from the mold and a device inserted through an orifice in the body for welding the element to the interior wall of the body. The element is then welded to this interior wall.