A degassing apparatus for use with a polymerisation reactor is disclosed. A first and second mezzanine card each having electronic circuitry defining a component field is mounted to the conduction-cooling path of the host card and connected to the connector assemblies. In response to the input signal, an output signal is generated from a predetermined area of the top surface and detected by a defect detector. A first hem in the first longitudinally disposed edge receives a first drawstring for loosely tightening the sheet material around the neck and a second hem in the second longitudinally disposed edge receives a second drawstring that tightens around the tail. The hinge is composed of a first hinge part and a second hinge part. The method is simple, quick and suitable for large-scale manufacture.