('informal') You need to 'get it into/through your thick skull' [=you need to realize/understand] that you can't just sit there and expect everyone else to do your work for you!
('informal') He can't seem to 'get it through his skull' that I don't like him.
He had a fractured 'skull'.
(..) when I meet him. And how will the great Durotan name his son? Better than you can hide your fat head. Laughing skull. Black rock. I just wonder who's left to fight? Lok'tar ogar! (Victory or death!) (..)2016 Warcraft