use your loaf

used to tell someone in a slightly angry way to think more carefully about what they are doing

(用于表示对某人思考问题欠认真而稍为恼火时)多动动脑子，好好想想

在第一次世界大战中，士兵们会挖战壕，躲在里面几天，直到枪声减少或停止。这时，如果士兵想出来，他不可能直接冒头，所以就想出了先用一块面包伸出来，测试一下看看狙击手是否还在附近。loaf本意“一条面包”，后来就引申为脑袋的意思。

Use your loaf.

Use your loaf of bread.

Bread = head.

Use your head.

Jenny finally remembered to bring the right books home to do her homework. I'm glad she's finally using her loaf.

珍妮终于记得带对的书回家做作业了。我很高兴她终于动脑子了。