class Trade < ActiveRecord::Base

     has_and_belongs_to_many :tags

class Tag < ActiveRecord::Base
    set_table_name "tags"
    has_and_belongs_to_many :trades

end

how to i add records to the table tags_trades using active rcord. i
dont have a model for  tags_trades  becaues the docs states that i
dont need one.

thanks in advance.