A material which exhibits auxetic characteristics and control of thermal expansion characteristics while experiencing significant stress reduction is disclosed. The material has a repeating pattern of void structures along both lateral symmetry lines and longitudinal symmetry lines.

A flat harness is machined by providing a punching machine that includes a first punching device and a second device, and forming different types of hole portions in the shape on the insulating portion of the flat harness in a die cutting process by using the first punching device and the second punching device.