낫 놓고 기역자도 모른다
Lay down a sickle and still not recognize the letter ㄱ.
Used to describe a very ignorant person.
The Korean proverb suggests that if a person lays down a sickle and still cannot recognize the letter ㄱ, then that person is very ignorant since the shape of the letter ㄱ and a sickle are similar.
Not know A from B.