Prongs 80 and 82 are formed of a flexible material, such as plastic or the like, and can include a weakening hinge, such as hinge 120 in prong 82, whereby prongs 80 and 82 move outwardly and away from corresponding prongs 84 and 86 to permit first and second mating prongs 98 and 100 to move past gap-covering elements 94 and 96 and then move back to position gap-covering elements 94 and 96 over gap