know one's arse from one's elbow
English edit
Verb edit
know one's arse from one's elbow (third-person singular simple present knows one's arse from one's elbow, present participle knowing one's arse from one's elbow, simple past knew one's arse from one's elbow, past participle known one's arse from one's elbow)
- (Commonwealth) Alternative form of know one's ass from one's elbow