It is well known that in the general context the similarity relation is very fuzzy and hard to define. Unfortunately, the intuitive notion of similarity is not a transitive relation: knowing that A is similar to B and that B is similar to C does not necessarily imply similarity between A and C. This is a main obstacle when trying to express formally what a coherent font design is. The authors suggest a method to decompose complex letter forms into simpler elements and suggest a formal transitive definition of a similarity relation between these elements. In the context of digital typography, this definition enables developing an algorithm to recover classes of similar elements within different characters of a given font. This knowledge is further exploited to ensure coherent type processing. For example, a modification (e.g. by a type designer) of a character element is propagated automatically to all the other characters that include a similar element. For the moment, the discussion is limited to the class of stroke fonts