Abstract: A closed liquid container of thermoplastic synthetic-resin material is fod by blowing and comprises at least one construction element disposed within the container and secured to the wall thereof for dividing the inner space of the container into sections. The apparatus for the production of the container comprises a form tool, and a driving means moving the form tool into an open and closed position, respectively. A tube-forming head of an extruder is disposed on top of the form tool and at least one holding mandrel is movable in axial direction. The mandrel has at least one receiving element for a construction element and is disposed end-sided to the form tool in the head of the extruder.