Forms a tubular shirt, which is a shirt where the hips and chest are the same width and connected by a straight seam. Set this to true for front and back parts that are perfectly rectangular below the armholes. This setting overrides any values set for the hips ease or side shape options. For most body types, leaving this option on will result in a reasonable fit that is looser around the belly and tighter around the chest, and generally produces a more fabric-efficient pattern.