Pictograph of a tree (trunk, branches, roots) sits at the very bottom — the 'wood' the palisade is made of. The middle band of strokes is a fused historical residue related to
塞 'to stuff/block', which historically would split into 'walls + bricks' but in modern
寨 is too contracted to expose as a separate clean component, so it's grouped here with
木 as the wooden-palisade body of the char.