Not Too BrightOne worth keeping
“He's dumber than a sack of hammers.”
Dense. All weight, no sharpness.
In the same vein
All Not Too Bright →Looks alert. Isn't.
Not enough sense in there to do the smallest job.
Can't manage even the simplest task.
Not sharp at all.
He's lost whatever sense he had.
Can't tell the most basic things apart. Even a dog knows those two.