A standalone curtain holder that suits better for flex materials. The black part in the picture is printed with TPE. 

It also works for non-flex materials like PLA (as the green one in the picture), just functions differently. However, non-smooth surfaces on a hard part could harm the fabric.

There are two models with different dimensions: one has 20 mm in Z and 80 mm in X; another has 13 mm in Z and 90 mm in X.