So, someone may say, " Well, I'm going to put this in my circular file, " that is I'm going to throw it away.
所以，有人可能会说，“好吧，我要把这个放在我的回收箱里，”就是说我要把它扔掉。
ESL 露西的一天
Many times, we would joke about putting some of the sales paperwork into the circular file because it was more work for us to have to read it.
很多时候，我们会开玩笑地说，把一些销售文件放入回收箱中，因为还有很多内容等着我们去阅读。
英语百科
File 13
（重定向自Circular files）
"File 13" is a euphemism for the trash can. The phrase is especially used in the U.S. military, and is less common outside of the United States. In the United Kingdom, for instance, the expression "round file" or "circular file" is more common (in reference to trash cans typically being round). Expressions such as "I'll place that memo in file 13" are often heard in offices as a joking way of saying, "I'm going to throw away that memo."