Roman Guilds
One of the Roman's secrets of success was their use of guilds. Almost all Roman builders came from guilds, each with their own name, such as the citrarii, or carpenters. Within the guilds, knowledge of materials, techniques and tools was kept and passed down from generation to generation. On top of this there were Roman building contractors who coordinated the various guilds in the construction of the buildings.
Along with this, the guilds, such as carpenters, stone masons, and metal workers were trained to make the Roman Legions self-supporting. Standards were introduced into the Legion for control, and with these, the Legion built military and civilian roads, fortifications, bridges, and other needed products. Before the soldiers retired from active service, their craftsmanship was transferred to their successors and to workers from local communities. In this way, the Legion was more than simply a fighting unit. It was also a construction and engineering unit.