jQuery is required.

In the Gemfile
  gem 'sortable_nested_set'

In each "Category" model (e.g. "Directory"):
  acts_as_sortable_nested_set_of :items
where :items is the pluralized Item model (e.g. "File").

In each "Category" controller:
  handles_sortable_nested_set
to include menu actions.

In the routes config file:
  sortable_nested_set_for :categories
for each pluralized "Category" model.

In each "Category" migration:
  name:string
  lft:integer
  rgt:integer

In each "Item" migration:
  position:integer

Helpers:
  sns_options
  sns_lineage
  sortable_nested_set_tree