Frequently it happens that during symbols recognition, not all of them are the proper ones. This may cause deterioration of a classifying process. In this paper we present a way to “separate the wheat from the chaff”, by constructing a rejector, based on geometrical figures enclosing “wheat” and excluding “chaff”. We assume that entities of wheat, called native elements, are structured in some way and that there is no a priori knowledge about chaff, named foreign symbols. For the purpose of this study we present simple geometrical figures to generalize the distribution of symbols and to govern the rejection process.