Modern scholars usually examine what the municipal charters tell us about the local administration, the legal processes etc. They are annoyed whenever the texts – using only references or ambiguous terminology – do not explain something that is not known to us. It is much rarer for them to examine whether the average inhabitant of a city was able to understand the legal topics which are obscure even for modern jurists. In this paper I try to map the knowledge necessary to understand and apply the municipal charters.