请问这是should的特殊用法吗？

should在句子 It is understood that her cloest advisor will take over as president should she resign early.里的意思？
请给举其他例子说明。谢谢！

这里的should在虚拟条件句中用以加强假设语气，用"should+do"指将来的情况，当"万一(会)"讲,这句话if省略，should作为情态助动词提前了，所以比较难懂。
原句应该是：It is understood that her cloest advisor will take over as president if she should resign early.
意思是：一旦她提前辞职，她最亲密的顾问就会接替她成为总裁，这也是可以理解的。
类似例句：①Should it rain tomorrow, I should/ would stay at home.万一明天下雨的话，我就待在家里。
②Please call me should you need my help.万一需要我帮助的话，请给我打电话。(此句中should need可用need代替。)
希望我的讲解能帮到你。

特殊的虚拟语气词：should

1） It is demanded / necessary / a pity + that…结构中的主语从句的谓语动词要用should 加动词原形， should 可省略。

句型：
(1)suggested
It is (2)important that…+ (should) do
(3) a pity

(1)suggested, ordered, proposed, required, demanded, requested, insisted； + (should) do
(2)important, necessary, natural, strange
a pity, a shame, no wonder
(3)It is suggested that we (should) hold a meeting next week.

It is necessary that he (should) come to our meeting tomorrow.