You can hit the sack.

　　关于俚语“hit the sack” 的故事：

　　美国大兵把他们的睡袋称作sacks，去睡觉就成了去麻袋里。因此，hit the sack由此而流传出来。

　　ring a bell 想起，忽然有了模糊的记忆

　　常常指想起某件很熟悉的事情，以下是个例句：

　　A：Do you know the girl who was talking with Dan?

　　B: I can't remember her name but her face rings a bell with me.