The term roughing in implies that this stage is crude, and in some ways that is correct. At this stage of the building process, the main conduits for heating/cooling (called HVAC; heating/cooling, A/C), electrical and plumbing work are assembled and snaked through what will eventually be the walls and floors and ceilings. Other commodities, such as security systems, cable TV, or computer networking, should also be roughed in at this stage. It makes the most sense to tackle this work now, because the walls are open and exposed, and therefore workers can route cabling or conduit around relatively unimpeded.