any of the walls or surfaces of the frame receptacle 5 and the ends of the pivot shaft 18 partially underlie the overhanging receptacle lips 9 this avoids any clanking noise during the passage of vehicles and prevents the lug from being vertically lifted out of the receptacle when the cover is rotatably lifted from a point diametrically opposite the hinge lug the shaft 18 swings downwardly into engagement with the sloping bottom surface 12 of the receptacle from which it slides downwardly until its ends are supported solely by the surfaces 13 as seen in fig9 when the cover is rotated to a vertical position it may be removed as shown in fig8 if it is rotated further to an angle of 15 u00b0 20 u00b0 to the vertical a stable rest position is reached with the lug neck 17 bearing against the upper edge of the frame wall 11 and the ends of the pivot shaft 18 engaging the undersides of the lips 9 as seen in fig7 referring to the alternate embodiments shown in fig1 through 12 wherein the primed reference numerals designate components and features differing only slightly from their counterparts in fig1 9 the trough 7 39 is here configured to include a central region 21 extending radially from the receptacle neck 6 to the external wall 11 of the frame 1 39 and having a flat horizontal base 22 and two lateral areas 23 flanking the central area each lateral area has a base 24 disposed at a level higher than.