shù
=
shu
+
Ø4:
vertical stroke (in Chinese characters), referred to as 豎筆|竖笔[shu4 bi3]
Mnemonic
Mnemonic symbol: a dinosaur bone. Sheldon Shrimp (shu) found a gorgeous dinosaur bone (丨) in the space station's bathroom (Ø4) and is cracking it open to eat its bone marrow.