seamy side

Before I Say Good-Byeを読んでいます。
The wrapping paper and twine were in Winifred’s file--she remembered that clearly. She also knew that Winifred was involved with someone named Harry Reynolds, although she still had no clue as to who he was. Winifred had been at Walters and Arsdale for over twenty years, long before Adam went there. When she began working closely with Adam, had she taken advantage of his trust? Nell wondered. He would have been the new man on the job, untried and untested, while she knew the construction business, including the seamy side, backward and forward.
"seamy side" は文字通りには縫い目側ですが、ここでは一体何を指しているのでしょうか？　辞書を見ます。
・Dictionary.com: The sordid, unattractive aspect of something: "Lying and stealing are part of the seamy side of life.": The seamy side of British democracy was appropriately symbolized.
・Bartleby.com: The “wrong” or worst side; as, the “seamy side of Australia,” “the seamy side of life.” Thus, in velvet, in Brussels carpets, in tapestry, etc., the “wrong” side shows the seams or threads of the pattern exhibited on the right side.: You see the seamy side of human nature in its most seamy attire.
なるほど、カーペットの裏側から来た表現ですね。