prop up, support, brace
撐 centers on physically holding something up or keeping it steady: propping up, supporting, or bracing against collapse.
撐 combines 扌 (hand) with 牚, which likely contributes the sound and the idea of pushing or supporting. The exact historical development of 牚 is uncertain.
The hand radical 扌 braces the right side 牚, which looks like a sturdy frame with a top cover and a base. Imagine a hand propping up a heavy wooden support structure.
For チョウ, picture a strong support beam named Chou holding up a ceiling: Chou -> チョウ, and the hand braces the structure.