Left: tree 木, right: vote, ballot 票 (I insert the ballot 一 through the slot || of the ballot box 口 on the altar 示: When I vote.) [標木 = ひょうぼく = marking pole]
Mnemonic
(The tree as a boundary marker:) The tree 木 in the west 覀 shows 示 that it is a signpost.
The upper stroke 一 can be seen as the horizon, with variations of sun 日 and two legs 儿, which stand for a downward motion: Below the horizon sinks the sun (at sunset) in the west.
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