Right side
章 supplies the sound: zhāng → zhàng with tone shift only.
章 originally pictured a knife marking ornament on jade — a tally or emblem. Same phonetic family:
彰 manifest,
樟 camphor. The phonetic also adds flavour to
障: a marked-off zone, a clearly bounded barrier — fitting both walls and figurative obstacles (
故障 malfunction,
屏障 screen).
