lip formation 96 which is flush with the lower surface 78 and extends from the short wall or wing 97 toward the extremity 92 and terminates far short thereof at an end 98 the axial length of the lip 97 is selected to be substantially less than the linear distance between wing 97 and wall segment 76 the lip 94 also is less thick than the latch bolt so as to provide a retainer overhang formation for the spring 46 as will be described the end 98 of lip 96 is spaced from the wall segment 76 so as to provide an entrant to the space below the overhang formation the wall segments 97 and 76 each have an end face which on the segment 97 functions as a stop for the end 100 of the spring 46 the end 102 of the spring 46 opposite the end 100 is placed against the spring stop member 76 the spring 46 is sufficiently long so that when the bolt 44 is installed beneath the cover 42 the spring 46 exerts a biasing force which maintains the bolt 44 projecting through passageway 64 once installed within the cover 42 the spring 46 is located in a pocket 106 defined by the underside of the cover 42 a side edge of the bolt 44 the.