What are work planes that allow the construction of 2D sketches on complex 3D models referred to?

The correct term for work planes that enable the creation of 2D sketches on complex 3D models is "Sketch Planes." Sketch planes are essential in 3D modeling software, as they provide a surface on which designers can draw 2D profiles that will later be extruded, revolved, or otherwise manipulated to form 3D shapes. These planes can be oriented in various directions relative to the 3D geometry, allowing for flexibility and precision in the design process.

While "Construction Planes" may imply the use of additional reference planes for alignment or measurement, they do not specifically indicate the planes used solely for sketching. "Working Planes" is a less common term and can often be used interchangeably with sketch planes, but it may not adequately express the concept of creating actual 2D sketches. "2D Planes" suggests two-dimensional surfaces in a general sense, but does not specifically refer to their role within the context of 3D modeling operations. Thus, "Sketch Planes" is the most precise and commonly accepted terminology for these work planes in the context of 3D modeling.