Rust Marks on Patio Screening

Iron Out. Comes in liquid or powder, safe for fabrics, available at hardware stores, Wallyworld, etc.

Clicky

Elizabeth 24, I assume you are still in the Tacna area. That "rust" you are talking about, don't know what it is, but I believe it is in the dust that blows around, material gets damp and that seems to be what we end up with. I don't understand why it eventually congregates at folds but here in the Foothills we have the same thing. Folks that let the sunshade on all year and the RV stays here, it seems to roll to the edges.

Here's a link from the company that sells CLR which says that it's safe for fiberglass screens. Mix equal parts warm water and CLR. Apply with a sponge. Rinse thoroughly. I think I would test a small area first.