Dad said, "We used the plans your Mom and her co-workers designed to start building the beltline project. Most of the actual work on the roads and highways is performed by companies we call 'contractors.' The contractors are all experts at what they do. They operate the heavy machinery you see along the roads; the cranes, the machines that pour the pavement and mark the lines where the highways should be divided. As engineers, our job is to supervise and make sure the work is done the way it is written on the plans."