扁
biǎn , piān · HSK 6
flat
📏 扁 = 户 (door) + 冊 (tablet) — a flat plaque hung over a doorway
Originally a horizontal inscribed tablet mounted above a door, so the character carries the sense of flat. The 'beat sb up' slang piān/biǎn is a later colloquial extension — to flatten someone.
扁 — door 戶 on top + 册 (bamboo strips) below
扁 originally depicted a wooden tablet or plaque hung above a door (戶) inscribed like bound bamboo slips (册), used for signs or inscriptions. From 'flat tablet' it generalized to mean 'flat' or 'thin'. The reading piān ('small, slender') reflects this same flatness sense.