Solid modelers enable engineers to design 3D objects including free-form surfaces, and solid models can be used for many systems such as CAM and CAE. However, solid modelers are generally too expensive comparing to 2D CAD systems, and it is difficult and time consuming to create the solid models of products consisting of a great many parts. In this case, the products can be expressed simply in 2D CAD systems by using simplified expressions such as omissions and sectional views. In this paper, a method is proposed that can convert 2D drawings of structures including omissions and sectional views into 3D models. The properties of simplified expressions are formulated as an algorithm in the method.