rocks in one's head, have

have rocks in (one's) head

To be thoroughly stupid, crazy, absurd, incorrect, etc. You must have rocks in your head if you think the bank will approve you for another loan.
See also: have, head, rock

rocks in one's head, have

Show poor judgment, act stupidly, as in If you think that's an accurate summary, you've got rocks in your head. The rocks in this idiom are a supposed substitute for brains. [Slang; 1940s]
See also: have, rock