OptionalidName of the part within its model.
OptionalrotationTurn around the vertical axis applied to the part's shapes, in degrees.
OptionalcenterPoint the part's shapes were moved to.
OptionalscaleScale factor along X, Y and Z applied to the part's shapes.
OptionaldirectionDirection the part's up axis was turned to point along.
The base of every named part of a finished model: an id and the placement the model applied to the part's shapes. A part class extends it with the shapes it holds.