know one's ass from a hole in the ground

Verb

 * 1)  To have an adequate level of knowledge or skill; to understand what one is doing or talking about.

Usage notes

 * Almost always used in negative constructions to describe someone's ignorance or stupidity, such as: He doesn't know his ass from a hole in the ground.

Antonyms

 * See

Translations

 * Jamaican Creole: know weh 'im fa
 * Spanish: estar más perdido que un pulpo en un garaje, estar más perdido que un calamar en un pajar, confundir la velocidad con el tocino