certificate_magic.rb

module CertificateMagic
  def self.included(base)
     base.send :extend, ClassMethods
  end

  module ClassMethods
    def some_class_method
    end
  end 

  def instance_method_one
  end

  def other_instance_method
  end
end


....

class AwesomeCertificate < AR::Base
  include CertificateMagic
end