To grind a brick into a mirror; a metaphor for an impossible or futile endeavor, indicating that one's efforts are destined to fail.
他想靠临时抱佛脚就通过考试，这简直是磨砖作镜，白费力气。
He tried to pass the exam by cramming at the last minute, which is like grinding a brick into a mirror, a futile effort.
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