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If you have the grain going the wrong way the paper will ripple, the fold will not be clean and the book will want to close itself.
如果把纸的纹路弄反了，纸就会起皱，折边也不整齐，书还总是会自己合上。
youdao
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A wrinkle, ripple, or fold.
皱纹，波状，褶痕。
youdao
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A wrinkle, ripple, or fold.
皱纹，波状，褶痕。
youdao