the surface then the average wall to wall distance can be determined in any one direction across the surface where the pores are generally oblong in cross section as ellipses or rectangles if the pores are oriented randomly at the surface then the average wall to wall distance can itself be an average of an average of distances determined in any two or more directions across the surface where the pores of any type are arranged in a substantially regular pattern at the surface the average wall to wall distance can be determined from the concomitant substantially regular arrangement of pore walls thus e g where the pores are generally oblong in cross section and are oriented at the surface with their main axes generally parallel the average wall to wall distance can be determined by measuring pore wall center to center distance across either the major axes or the minor axes thereof similar principles apply to determine useful average wall to wall distances for use with other pore arrangements in various embodiments in which surface pores of a substrate are spaced further apart such that the pore defining walls present at the surface are wider the rows of a coordinately deposited layer can be wider than those used in embodiments in which pore defining walls present at the surface of a substrate are narrower where.