The surfaces can now be created. Four corner points are needed to create a surface, and CopyCAD takes the shortest route between two points. The curves you have just created will be used as a guide to create the first surface.
To do this
on the Main toolbar to display its side toolbar.
on the side toolbar. This puts you in Surface Creation mode and opens the Curve and Surface Fitting Options dialog box. We are going to use the default settings in this dialog box to create our curves. Note: Advanced users can change the Curve and Surface Fitting options to suit the particular needs of a model.

The selected points are shown as yellow squares, with purple lines connecting them.
When you re-select the first point, the surface boundaries are closed and the first surface is created. The model will look like the one below. The surface has a surface marker on it, which you can use to select it.
on the Draw toolbar. The model looks like this:
Creating a Surface using Guidepoints