What do you throw out when you want to use it,but take in when you don't want to use it

问题描述:

What do you throw out when you want to use it,but take in when you don't want to use it

你问什么呀? 是意思还是谜底?

什么东西当你想要用的时候将它丢掉,而不用的时候将它拿回来?