A finite rank Butler group G is a torsionfree Abelian groups that is the sum of m rank one subgroups; G is a B ( n ) -group if n is the maximum number of independent relations between the m subgroups. After the well-known class B ( 0 ) , the much studied B ( 1 ) and the first approaches to B ( 2 ) , in this paper we generalize some of the tools used before and introduce new ones to work in every B ( n ) . We study some of the relationships between these tools, and while clarifying some basic settings describe an interesting class of indecomposables.