Each of the six riveters within the shop had an associated furnace (red arrows) for keeping the rivets hot. The process of riveting consists of inserting a red-hot rivet into a pre-drilled hole in the two flat pieces of metal to be joined. A pneumatically-driven die in the riveting machine forms a head on the plain end of the rivet, and the two pieces are drawn even more tightly together as the rivet cools.
Prior to industrial welding, riveting was the primary way that metal forms were made. Almost all the components of a truss bridge were made by riveting together plate, bars, and angles. Because many of the company's bridges were intended for rural areas, where it was difficult to ship large components, big pieces such as the top chord were fabricated in sections, then joined in the field using bolted connections in place of rivets.