Bamboo radical on top — bamboo-cap form of
竹 — marks
筐 as a bamboo-woven object. Traditional Chinese baskets are still made from bamboo strips. Same top-form radical drives
笔 (brush),
答 (answer),
篮 (basket),
笼 (cage),
筷 (chopsticks). All bamboo-product chars share this six-stroke cap.