If someone is as thick as two short planks, it means they are very slow to understand things or seem quite foolish. The phrase is usually used in a joking or slightly rude way to say that someone is not very clever.
The idiom compares a person's thinking to two pieces of wood, suggesting there is not much going on in their head. People often say it in a playful or sarcastic tone when someone misses something obvious.
The idiom compares a person's thinking to two pieces of wood, suggesting there is not much going on in their head. People often say it in a playful or sarcastic tone when someone misses something obvious.
I had to explain the instructions three times before he admitted he felt thick as two short planks.