don't know your ass from a hole in the ground
It means you don't know any better or not up for the job.
Son you don't know your ass from a hole in the ground What makes you think you can do this?
you don't know your ass from a hole in the ground
Figure of meaning that someone doesn't know what they're doing.
You don't know your ass from a hole in the ground.
you don't know your ass from a hole in the ground
"You don't know your ass from a hole in the ground." Illustrate with a pen and paper drawing a circle and a cracked circle. Now ask which is your ass and which is the hole in the ground. Subject points to cracked circle and you mock while pointing to their real derriere.
After listening to untruthful gibberish, you say to person, "you don't know your ass from a hole in the ground."