nawaami ナワアミ

In manga, nawaami ナワアミ, "rope net," is the term the ropes drawn in the background of panels.

They're also called kake-nawa カケナワ, "thrown rope," guriguri グリグリ, and hebinawa ヘビナワ, "snake rope." Some of its names come from the fact that they're drawn using the same technique as kakeami カケアミ.

Manga: Black Jack, ブラック・ジャック (Chapter 1, 報復)

• Examples
• References

Examples

For reference, some examples:

Manga: Gotoubun no Hanayome 五等分の花嫁 (Chapter 1, 五等分の花嫁)

• mu'
  ムッ
  *annoyed, huffy*
  
• fukurettsura
  ふくれっ面
  Face puffing cheeks, pouting.

Manga: Black Jack, ブラック・ジャック (Chapter 1, 報復)

• ...okuyami wo tsutaete kudasai
  ･･･おくやみをつたえてください
  ...communicate my condolences.
• makoto ni zan'nen desu to
  まことに残念ですと････････････
  [Say] that [it was] truly unfortunate............
  [Say] that [I'm terribly sorry for what happened]............

References

• [まんがを描こう！]カケアミとカケナワ（ナワアミ）のやり方ご紹介（グラデーション追加しました） - lanmy.net, accessed 2020-02-27.
• きたがわ翔のアナログイラスト講座（７）背景はナワアミを全体に描いていきます　ナワアミ解説編 - creators.yahoo.co.jp, accessed 2020-02-27.