teaching grandma to suck eggs
Teaching some process which should already be known, especially to a person who should already know it.
"What does this woman think she's doing? Teaching multiplication to a Calculus class is like teaching grandma to suck eggs!"
Grandma's Eggs
The exquisite smell of shit pipes. Hearty and full of chunky turds the smell seeps from the corroded pipe walls reminding you of the horrible stench of your late babushka's breakfast eggs.
I haven't been to any breakfast joints since we got a whiff of Grandma's Eggs. Just the sight of an egg makes my nose hairs curl...