fence, hedge
墻 centers on a barrier made of earth or plants: a fence or hedge that encloses or divides space.
墻 combines 土 (earth) with 嗇, a component that likely contributes the sound and relates to enclosure or storage. The character originally referred to an earthen wall or fence.
The left side 土 (earth) suggests a barrier made of piled earth, while the right side 嗇 looks like a fenced enclosure with a roof. Together they form a fence or hedge.
For ショウ, imagine a show garden surrounded by a neat hedge: show -> ショウ, and the fence keeps the display perfect.
parapet; breastwork