head 130 which is deformed in order to trap the leaf 12 b u2032 to the second lateral bar 112 wherein the cooperative noncircularity of the shank 122 with respect to the bar and leaf holes 124 126 prevent the second lateral bar from rotating around the rivet axis r u2032 with respect to the shortest leaf 12 b u2032 a bolt 132 has a bolt head 134 and adjoining non circular bolt portion 136 in the preferred form of a bolt neck 136 a having a non circular cross section the non circularity being for example oval rectilinear preferred or otherwise non circular as for example having an axial keyway or key the preferred bolt 132 is a carriage bolt with an elongated square cross sectioned bolt neck as shown a threaded bolt portion 138 is threadable with a nut 140 as shown collectively by fig3 5 and 7 at the first superposition 116 a the first leg 110 a at its respective offset leg end portion 106 a and its abutting second leg 114 a have formed therein a mutually aligned first leg hole set 142 wherein each non circular leg hole 144 a 144 b thereof has the same non circular cross section which corresponds to the size and shape of the non circular cross section of the non circular bolt portion 136 such that the bolt neck.