Recent publications have used the impact of area change coupled with conservation of adsorbed catalyst to quantify the "superfill'' effect of bottom-up feature filling during electrodeposition and chemical vapor deposition. This work describes how that superfilling process can be quantified using planar fronts that grow from corners where surfaces impinge. The results obtained apply only when catalyst is preadsorbed on the surface, with no subsequent accumulation or consumption. However, because they are exact solutions, they can also be used to check the accuracy of models and computer codes concerned with the more general problems of feature filling. Implications for sidewall deposition associated with the incubation period are discussed. (C) 2003 The Electrochemical Society.