I need guidance regarding 3D modelling in CST. I have a 3D polygon (a strip) that is varying in width (along the x-axis) and in height (along the y-axis) and the length of the device is along the z-axis. I want to extrude this 3D polygon to a certain thickness like 35 um to make it a thick strip. When I use the option extrude in CST it returns an error "The selected curve is not closed or planer" please guide me on how to extrude such polygon.