No, it's a simile. An example of a synechdoche would be "All hands on deck," except in those rare cases when one is playing bridge on the deck of a ship and you want everyone to put all of their cards down.
One example might be " as tricky as a box of monkeys".Another example is "as dumb as a box of rocks".
it means that the box of rocks didnt listen anything and the person in this phrase is compared with box of rock
...a box of rocks. ...a bag of hammers. ...a fence post. ...a Dodo bird.
It means really dumb!
No
The oldest simile for 'as dumb as' is 'As dumb as a doornail'. Others include: As dumb as a wet noodle. As dumb as an unpowered computer. As dumb as a library with no books.
No. Box does rhyme with rocks, though.
boulder holder
because there dumb
rocks
boulder holder
The population isn't exactly dumb. It may seem that way if you are very intelligent. Also if you are talking to an un-educated crowd they would seem dumb to you. A lot of things can be blamed for the un-education though: Poor schools, Poor teachers, Poor parents, Non motivated children, Bad neighborhood or bad influence. But these are just excuses really. None of these can be truly called "the reason for un-education".