have enough sense to pound salt
To have a basic level of competence, intelligence, or common sense. Used most often in the negative to imply that someone lacks even that. A variant of the more common expression "have enough sense to pound sand." I lost my faith in the political process when I realized that the people getting voted into Washington don't have enough sense to pound salt. That boy doesn't have sense enough to pound salt. What makes you think he'll be able to fix your computer?