  In this paper we explore some applications of a certain technique (that we
call the Freese's technique), which is a tool for identifying certain lattices
as sublattices of the congruence lattice of a given algebra. In particular we
will give sufficient conditions for two family of lattices (called the rods and
the snakes) to be admissible as sublattices of a variety generated by a given
algebra, extending an unpublished result of R. Freese and P. Lipparini.
