The cost of materials is often a major part of the total cost of thin film products such as solar cells. When evaporation is used to manufacture a thin film product, the material cost depends upon the efficiency of material utilization which, in turn, depends upon the vapor source distribution and the portion of the vapor stream that is condensed on the substrate. The vapor incident on a flat substrate suspended and conveyed over single and multiple evaporation sources is analyzed. The sources are assumed to have symmetric vapor distributions described by fcos⊕ + gcos3⊕(P. The results are then applied to the design of masks which attenuate a portion of the vapor stream to provide a coating with uniform thickness. Graphs of the material usage efficiencies are provided for common configurations.