A Quad Surface can be created numerically by using the New Quad Surface dialog window (below), which specifies surface type, a list of Boundary Curves defining the surface, and its number, and has a box for possible comments or a description. A surface is a closed two-dimensional domain that is either the computational domain for two-dimensional applications or the base surface that can be extruded into a solid for three-dimensional applications. A Quad Surface is defined by the List of Boundary Curves. It can be created either graphically or numerically. Before using the New Quad Surface dialog window, users must first define Boundary Curves which are then used to define the Surface. Boundary Curves defining the Surface are entered in the List of Boundary Curves.