One, two, three. Dig a trench. Erect the precast wall panels in the trench. Then fill the trench with concrete. Erecting walls for a one- or two-story building is that simple with a patented precast wall system being introduced now. The key to the system is an opening near the base of each wall panel. Filling this opening with concrete at the same time the trench footing is cast ties the footing and panel together. This eliminates welded connections between the panels and the footings. It also creates a stronger connection.