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to shave off (esp. concrete)
to take a percentage; to take a cut
「削る」 has another reading with different meanings.
壁のコンクリートを電動工具で削る作業を始めた。
We started the work of scraping concrete off the wall with a power tool.
壁の表面を削って下地を出した。
I scraped off the wall surface to expose the base.
床を少しだけ削った。
I scraped off a bit of the floor.