Mnemonic symobl: a nail. 一 is the head of the nail and 亅 is the shaft. The point of the nail is already a bit bent.
Dorothy Gale (di) balances a flute (一) on a crowbar (亅) in front of the engine ((e)ng1). For this trick, she wins the fourth (丁) place in an artists competition and gets a quarter (丁) of a pizza as prize. Unfortunately, there is a big nail (mnemonic symbol for 丁) on the pizza slice.