I'm thinking you mean the manufactured ones like
https://www.collectionsetc.com/produ...bunting-banner
https://www.amazon.com/Beistle-S5094.../dp/B072Y7H9LG
https://www.orientaltrading.com/patr...-13730485.fltr
Those just look like strips of fabrics with casing type drawstrings. I found
https://media.iwm.org.uk/loris/8/289.../0/default.jpg that looks like it is straight across the top, and only a portion is drawn up to make the scallops. Also one could make something like curtain tiebacks but instead of on the side it would draw up to the top.
Another type would be like
https://www.thepaintedhinge.com/2015...ntingtutorial/
Janey - Neat people never make the exciting discoveries I do.
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