In 2D CAD systems, you think of projecting the views of a 3D model onto the sides of a glass box to visualize the 2D drawings. If you have a 2D model, or are designing in 2D, think in the opposite direction. Visualize the 2D drawings folded up onto the sides of the glass box and projected into a 3D model.
The following example started as a 2D drawing and was converted into a 3D model.
