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1·If seams are not fell flat, you must ensure seams are serged to cover the raw edges.

如果接缝不是外包边，必须确保缝头锁边。

2·If seams are not fell flat, you must ensure seams are serged to cover the raw edges and thus prevent raveling.

如果接缝不是外包边，必须确保缝头锁边并遮住毛边防止散边。