know one's arse from one's elbow

knew one's arse from one's elbow knowing one's arse from one's elbow known one's arse from one's elbow knows one's arse from one's elbow 三单 knows one's arse from one's elbow knowing one's arse from one's elbow 现在分词 knew one's arse from one's elbow 过去式 known one's arse from one's elbow 过去式 known one's arse from one's elbow 过去分词