A sheet blank for forming a collapsible field director structure comprises a sheet of nonconductive material having at least three panels thereon, one of the panels being a master panel and the other two panels being slave panels. Each panel is substantially rectangular in shape and has elongated upper and lower edges and two relatively shorter side edges. Each panel is connected to at least one adjacent panel along an elongated edge.A patch of adhesive material is disposed on: the first surface of a first one of the panels; and another patch of adhesive material is disposed on: the first surface on one of the other panels or the second surface of said first one of the panels. The slave panels are each foldable along an elongated edge thereof so that a surface of each of the slave panels is brought into confronting facial adjacency to and adhered against a surface of the master panel.