It is a seamless pattern of wire mesh (net). 金網(ネット)のシームレスなパターンです。

It's hand-painted and a bit cumbersome, with a wire mesh pattern.
If you throw it into a selection, you can draw wire mesh easily wherever you want!
There are also a set of ten kinds of materials including the material of this place.
https://assets.clip-studio.com/ja-jp/detail?id=1961255

手描きだと少し面倒な、金網のパターンです。
選択範囲に投げ込めば、お好きなところに楽々金網が描けます!
こちらの素材を含め、10種類の素材が入ったお得なセットもあります。
https://assets.clip-studio.com/ja-jp/detail?id=1961255