Conical Hat
A bamboo thing you put on your head to stand taller would probably be a hat. A bamboo hat is probably one of those hats you think of when you think of rice farmers, a conical hat.
You know the ones I'm talking about? They're cone-shaped, sort of, and they go on your head, keeping the sun off your face.
りゅう
かさ
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A conical hat is kind of like an umbrella on your head. What's the reading for "umbrella" in Japanese? Why, it's kasa (かさ)!
Think about a bamboo umbrella on your head. They're pretty similar in shape, after all.