用不了

用 = 丨 + 月 : Mnemonic symbol: a first aid kit. Can you see the cross on the container?

用 = 丨 + 月 : Yu the Great hurt her leg when she slipped in the engine's bathroom. The moon helps her to splint her leg using the bathroom's first aid kit and a dinosaur bone.

不 = 丆 + 卜 : Bruno Bear (bu) is setting up a wind wheel (丆) with a voodoo staff (卜) in the space station's bathroom (Ø4). He also puts a "forbidden" sign (mnemonic symbol for 不) on it, to make clear that it may not (不) be stopped.

了 = 乛 + 亅 : Sir Lancelot (l) has completed (了) his preparations to fight the world. There he stands ready, on top of the Elevator (e5), with a sickle (乛) and a crowbar (亅) in his hands.

了 = 乛 + 亅 : Mnemonic symbol from "to finish" and the shape of the character: a prize cup.

Li Qingzhao (li) is responsible for manufacturing a prize cup (了). She only needs to add a poetic engraving. Unfortunately, she suffers from a writer's block. In the aorta's living room (ao3), someone left a cryptic message engraved on the walls using a sickle (乛), which is still lying on the floor. Being an accomplished poet Li Qingzhao is able to understand the message clearly (了), realizes its poetic potential and starts to engrave it on the prize cup using a crowbar (亅).