the sharp edge of a knife 刀刃 Oxford Collocations DictionaryKnife-edge is used before these nouns:- vote
Idioms
on a knife-edge
(of a situation, etc. 形势等 in a difficult or dangerous situation in which a very small change can cause somebody/something to succeed or fail 胜负难料；成败未定 (of a person 人 very worried or anxious about the result of something 十分焦虑；急于知道结果 He’s living on a knife-edge, waiting for the test results. 他生活在危险之中，等待着测试结果。