    # File lib/rubygems/package/tar_writer.rb, line 138
      def mkdir(name, mode)
        check_closed

        name, prefix = split_name(name)

        header = Gem::Package::TarHeader.new :name => name, :mode => mode,
                                             :typeflag => "5", :size => 0,
                                             :prefix => prefix

        @io.write header

        self
      end