Smartest Tool in the Shed

This phrase is a combination of the two phrases: the smartest guy in the room, and the sharpest tool in the shed. The phrases are practically identical in meaning, so combining the phrases is a move of a literary genius. The phrase: the smartest tool in the shed means the smartest tool in a hypothetical shed.

He’s not the smartest tool in the shed, it takes him a little bit to understand.

He might be the smartest tool in the shed, but that doesn’t make him a good person.