ends of the meshing elements 13 are somewhat more yielding than the regions immediately at the foot of the meshing elements 13 for example the inner conical angle w1 is approximately 40 u00b0 for the two embodiments of fig7 and 8 the outer conical angle w2 is approximately 70 u00b0 for the embodiment of fig7 and approximately 75 u00b0 for the embodiment of fig8 advisably the inner conical angle w1 is of the order of 30 u00b0 to 50 u00b0 preferably 35 u00b0 to 45 u00b0 and the outer conical angle w2 is of the order of 50 u00b0 to 90 u00b0 and preferably of 65 u00b0 to 80 u00b0 for the construction of fig6 the wall thickness s is practically constant over the whole length with the exception of the direct free end of the meshing element 13 the production of such a variation by a stamping process is also conceivable in which case the free end region of the meshing elements 13 so formed burst open slightly so that a roughening or corresponding cracks which increase the friction are formed or form at the free end of the meshing elements 13 in the case of the embodiment of fig8 it can be seen that a wave shaped or toothed limiting edge which in turn ensures a special friction increasing effect when used in the roofing sheet is formed at the free end of the meshing element from the geometry alone it can be seen that the construction of such quite special meshing elements 13 can be used not only for large area washers made from metal but also for washers produced from plastic by injection molding in the case.