This GCD represents the stock cross-section. Its properties include Area, Height (for rectangular stock), Outside Diameter (for round stock), Inside Diameter (for round tube stock), and Shape.

Note that the value of the Shape property is generally the same as the stock type (for example, SQUARE_BAR or ROUND_TUBE), but for plate stock (which has a rectangular cross-section) the value of the Shape property is RECTANGULAR_BAR.