knife on the line 71 see fig6 along the lower region of the preform and thence on the inverted u shaped line 72 whereby excess material can be removed leaving the void at the bottom of the preform 24 as shown in fig7 and thus enabling the preform to be removed from the mold 31 despite the undercut as at 73 it will be seen that the preform 24 now has the shape contour and configuration of the cover 11 in fig1 albeit inverted from that shown in fig7 the procedures described above have been determined to be necessary in order that there is produced on a consistant basis covers which are possessed of the advantages which are most desirable and distinguish my covers from covers presently on the market in a significent market share the procedure outlined has also been repeated numerous times and determined as definitive of the desireability of the sequence of steps the selection of materials and the process conditions are likewise verified by repeated efforts as confirm the reliability thereof and the operations as described for example elimination of the mesh stockings between the mold and the cone shaped preform yields a less desireable cover by reason of the presence of air pockets and air bubbles which while tolerable on the inside surface are totally unacceptable on the outside surface due to the visibility thereof detracting from the cosmetic appearance in addition the absence of the cotton and nylon socks would require an increase in time for the vacuum to.