boundary, border
畺 centers on a dividing line between areas: a boundary or border. The idea is a clear separation between two sides.
畺 is an older form related to 疆 (boundary). It visually combines 田 (field) with lines suggesting division, but the exact historical development is uncertain.
畺 looks like three 田 (field) shapes stacked with lines between them, as if marking the borders between different fields. The bottom 一 underlines the final boundary.
For キョウ, imagine a border guard shouting 'Kyō!' (今日) as he checks the boundary line: Kyō -> キョウ, and the border is marked.