private function writeSheetProtection()
    {
        // record identifier
        $record = 0x0867;

        // prepare options
        $options = (int) !$this->phpSheet->getProtection()->getObjects()
                    | (int) !$this->phpSheet->getProtection()->getScenarios() << 1
                    | (int) !$this->phpSheet->getProtection()->getFormatCells() << 2
                    | (int) !$this->phpSheet->getProtection()->getFormatColumns() << 3
                    | (int) !$this->phpSheet->getProtection()->getFormatRows() << 4
                    | (int) !$this->phpSheet->getProtection()->getInsertColumns() << 5
                    | (int) !$this->phpSheet->getProtection()->getInsertRows() << 6
                    | (int) !$this->phpSheet->getProtection()->getInsertHyperlinks() << 7
                    | (int) !$this->phpSheet->getProtection()->getDeleteColumns() << 8
                    | (int) !$this->phpSheet->getProtection()->getDeleteRows() << 9
                    | (int) !$this->phpSheet->getProtection()->getSelectLockedCells() << 10
                    | (int) !$this->phpSheet->getProtection()->getSort() << 11
                    | (int) !$this->phpSheet->getProtection()->getAutoFilter() << 12
                    | (int) !$this->phpSheet->getProtection()->getPivotTables() << 13
                    | (int) !$this->phpSheet->getProtection()->getSelectUnlockedCells() << 14;

        // record data
        $recordData = pack(
            'vVVCVVvv',
            0x0867, // repeated record identifier
            0x0000, // not used
            0x0000, // not used
            0x00, // not used
            0x01000200, // unknown data
            0xFFFFFFFF, // unknown data
            $options, // options
            0x0000 // not used
        );

        $length = strlen($recordData);
        $header = pack('vv', $record, $length);

        $this->append($header . $recordData);
    }