Simplify the following text for a Grade 6 native English-speaking person.
Original: Most modern Japanese castles have moats filled with water , but castles in the feudal period more commonly had ` dry moats ' ( karahori , ç å ) , essentially a ditch . Even today , it is common for mountain castles to have dry moats .
Simplified: Some moats , called dry moats , were instead filled with sharp pieces of wood called bungy sticks .