You shouldn't necessarily knocksomeoneoff who comes from a foreign medical school or an unknown school in the Midwest, but top-tier schools hae already done the legwork of weeding out people.
你不必看不起从国外医学院或中东一个不知名学校出来的医生，不过顶级学校确实有严格的筛选机制。
2
Knock it off, it used to tell someone to stop doing sth. that one finds annoying or foolish.
这个词组用于告诉某人停止做烦人或愚蠢的事，也就是“住手；别闹了”。
3
One man said that if someone was smiling at him for no reason he'd want to knock his block off.