public function setBorders(PHPRtfLite_Border_Format $borderFormat,
                               $left = true, $top = true,
                               $right = true, $bottom = true)
    {
        if ($this->_border === null) {
            $this->_border = new PHPRtfLite_Border($this->_rtf);
        }
        $this->_border->setBorders($borderFormat, $left, $top, $right, $bottom);
    }