Even if many architects start with pen and paper and later scan their drawings into CAD systems, they still need CAD software to design and communicate their plans to clients, engineers, and construction managers. However, with this solution, a new problem arose. In many ways, CAD is the perfect solution because it allows architects to turn their hand drawings into 2D and 3D designs and quickly fix problems that emerge. It also did not allow them to easily communicate their plans to construction managers and engineers. However, using pen and paper made it extremely difficult to catch errors in their plans. Then, they would build 3D models to illustrate their plans to clients. For years, architects would create their building plans using pen and paper.