According to myths and legends, a fairy's clothes are seamless. Metaphor things carefully perfect, can't find anything wrong.
source: Guo Han, a book by Niu Qiao, a former Shu: "Xu regarded his clothes as seamless, and Han asked him, saying,' Heaven's clothes are not a needle and thread.' "
Translation
Guo Han carefully admired the seamless integration of Weaver Girl's clothes, but he couldn't see a stitch. He asked Weaver Girl curiously. Weaver Girl replied," Tianyi clothes are not a needle and thread. "