An apparatus capable of assisting in controlling an electrolyte flow and an electric field distribution used for processing a substrate is provided. It includes a rigid member having a top surface of a predetermined shape and a bottom surface. The rigid member contains a plurality of channels, each forming a passage from the top surface to the bottom surface, and each allowing the electrolyte and electric field flow therethrough. A pad is attached to the rigid member via a fastener. The pad also allows for electrolyte and electric field flow therethrough to the substrate.