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screw
key (of a clock, watch, etc.); spring
この棚を組み立てるには螺子が何本か必要だよ。
You need several screws to assemble this shelf.
螺子が緩んでいたので締め直すことにしましょう。
The screw was loose, so let's tighten it again.
電動ドライバーを使うと螺子締めが楽になるね。
Using an electric screwdriver makes screwing easier.