One's brain, skull, or head. It's a good thing I was wearing a helmet when I fell off my bike, or I would have cracked open my knowledge-box! I don't know how you store so many facts in that knowledge-box of yours!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
n. the head. Now, I want to get this into your knowledge-box once and for all.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.