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the vertical; height
front-to-back; length
north-to-south
vertical (relationship); hierarchy
(weaving) warp
竪の線をまっすぐ引いてね。
Draw the vertical line straight.
竪と横を間違えてしまった。
I accidentally mixed up vertical and horizontal.
この布は竪に裂けやすいから気をつけて。
This fabric tears easily lengthwise, so be careful.