protected function _update($rght, $dir = '+', $span = 2, $scp = []) {
		extract($this->_config);

		$model::update([$right => (object) ($right . $dir . $span)], [
			$right => ['>=' => $rght]
		] + $scp);

		$model::update([$left => (object) ($left . $dir . $span)], [
			$left => ['>' => $rght]
		] + $scp);
	}