private function writeWsbool()
    {
        $record = 0x0081; // Record identifier
        $length = 0x0002; // Bytes to follow
        $grbit = 0x0000;

        // The only option that is of interest is the flag for fit to page. So we
        // set all the options in one go.
        //
        // Set the option flags
        $grbit |= 0x0001; // Auto page breaks visible
        if ($this->outlineStyle) {
            $grbit |= 0x0020; // Auto outline styles
        }
        if ($this->phpSheet->getShowSummaryBelow()) {
            $grbit |= 0x0040; // Outline summary below
        }
        if ($this->phpSheet->getShowSummaryRight()) {
            $grbit |= 0x0080; // Outline summary right
        }
        if ($this->phpSheet->getPageSetup()->getFitToPage()) {
            $grbit |= 0x0100; // Page setup fit to page
        }
        if ($this->outlineOn) {
            $grbit |= 0x0400; // Outline symbols displayed
        }

        $header = pack('vv', $record, $length);
        $data = pack('v', $grbit);
        $this->append($header . $data);
    }