How can I change its width?

Hi, again me!

I’m writing again as I’m looking for a better solution.

I have many polysurfaces like this;

I want to shorten these polysurfaces by six millimeters from the left and right.

I have tried many method; (Brep edges> offset curve/ offset surface or discontinuity> offset curve) but i can’t do this. Sorry for my questions, I’m new here&Grass.

Polysurfaces.3dm (84.8 KB)

one way is to make a _Cutplane through the dotted lines in your drawing, then _OffsetSrf that surface in 6mm and use that to _Trim the polysurfaces