get through thick skull

get (something) through (someone's) thick skull

To make someone or oneself acknowledge, accept, or understand something when they are or are being obtuse. Look, just get it through your thick skull: we're moving, and there's nothing that's going to change that now. I don't know how else to get it through her thick skull that I want to break up.
See also: get, skull, thick, through

get something through someone's thick skull

 and get something into someone's thick head
Fig. to manage to get someone, including oneself, to understand something. He can't seem to get it through his thick skull that he has to study to pass the exam. If I could get this into my thick head once, I'd remember it.
See also: get, skull, thick, through