cap member 26 thereon a conically shaped chimney member 28 extends upwardly from the top surface 22 of the top cover 14 as shown in fig2 the chimney member 28 includes a peripheral rim surface 30 and a generally flat circular surface 32 the circular surface 32 includes a centrally located primary opening 34 which is surrounded by a plurality of flexible flap members 36 the flap members 36 are formed by a plurality of equally spaced and radially outwardly extending slots 38 four equally spaced locking tabs 40 are positioned along the outer periphery of the circular surface 32 a pair of secondary openings which are generally rectangularly shaped 42 and generally triangularly shaped 44 respectively are opposingly positioned along the outer periphery of the circular surface 32 with both of the secondary openings 42 and 44 respectively being positioned between a pair of locking tabs 40 and outwardly from the outer end of a slot 38 the rectangularly shaped secondary opening 42 is a generally rectangular member having a pair of square shaped members which intersect the ends of the rectangular member such that the secondary opening 42 includes three distinct sections having three different widths the functions of which are described hereinafter as shown in fig2 5 the generally triangular shaped secondary opening 44 of the present invention includes a semicircularly shaped first area 46 and a triangularly shaped second area 48 which.