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lengthwise, lengthways
Yes, lengthwise is an adverb. It is used with verbs indicating positioning, measuring, or cutting.
because it is easy to do crosswise than lengthwise
You measured the frame lengthwise and then fastened it securely.
There are two adverbs in this sentence - lengthwise (modifying measured) and securely (modifying fastened). All other words are not adverbs.
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