This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
牅 is a rare character whose historical development is uncertain. It visually combines 爿 (left) and 庸 (right), but the original semantic and phonetic roles are unclear.
With no clear meaning, picture a forgotten fence (かきね) made of wooden planks (爿) leaning against a common structure (庸).
For ヨウ, imagine a yo-yo hanging on the fence: yo -> ヨウ, and the string wraps around the planks.