The basic shape of such parts is a flat disk shape, generally having end caps, bonnets, gears, etc., and their main structure is generally a rotating body, usually with various shapes of flanges, uniformly round holes. And local structures such as ribs. In the view selection, the cross-sectional view of the symmetry plane or the rotary axis is generally selected as the main view, and other appropriate views (such as the left view, the right view or the top view) are added to express the shape and the uniform structure of the part. A left view is added as shown to represent a square flange with rounded corners and four evenly spaced through holes.