A method for calculating electromagnetic scattering properties of a finite periodic structure having a direction of periodicity is disclosed. The sign may include a pair of walls that face in generally opposite directions so that messages can be displayed in two general directions, and a hook for hanging the walls from a support, such as a handrail assembly or other stanchion. The waistbelt may be attached to a backpack, as part of a backpack system, by straps that are directly affixed to the waistbelt. The bottom part of the notch is formed into the horizontal plane and the plug lid is supported while it is not inclined under application of weight and the packing is protected from unnecessary crushing force. In addition, the network itself is tailored to provide the best efficiency for remote accesses. The solution includes an aqueous copper salt component, an aqueous cobalt salt component, a polyamine-based complexing agent, a chemical brightener component, a halide component, and a pH-modifying substance in an amount sufficient to make the electroless copper plating solution acidic.