provided in the embodiments of fig3 and 8 to 10 furthermore both walls 12 and 13 of the wedges shown in fig1 and 4 have stamped out flaps or projections 18 which are bend inwardly or outwardly and provided near the edges having teeth 14 these flaps 18 form cut limiting surfaces which in turn limit the insertion of the toothed edges of the wedge into a lattice 19 of the lattice substructure and form wedge supporting surfaces as can be seen in fig8 to 10 wedge walls 12 and 13 of wedge 10 2 illustrated in fig3 are reinforced by stiffening corrugations 20 in the embodiment of fig5 walls 12 and 13 of wedge 10 3 are bent at right angles in the region of the toothed edges to form the cut limiting surfaces 21 furthermore an extension wall portion 22 of the wedge backside 11 is bent inwardly to form a transversal wall wedge 10 4 shown in fig6 is formed at the widened end thereof with bent in portions which form extension regions 23 and 24 or transversal portions of walls 12 and 13 both wedge walls 12 and 13 in this embodiment are bent at right angles in the regions of toothed edges 14 inwardly to form wedge surfaces 25 with reference to fig1 it will be seen that holes 16 in.