railing
柤 centers on a wooden barrier or fence: a railing. The meaning is narrow and concrete, referring to a structure made of wood that marks a boundary or provides support.
柤 combines 木 (tree/wood) with 且, which likely contributes a phonetic element. The character is used for a wooden railing or fence, but the exact historical development is uncertain.
A wooden 木 barrier that acts like a shelf 且: picture a railing made of wooden planks stacked like shelves to form a fence.
For サ, imagine a wooden railing in a serene garden: the sound of 'sa' in 'serene' cues サ while you lean on the railing.