As the County Fire tore through Northern California this summer well on its way to burning 90,000 acres in Napa and Yolo counties, Harley Ramirez got a call. The 132nd Multirole Bridge Company of the California National Guard was heading toward the blaze, and Sergeant First Class Ramirez was being put in charge. His team’s mission: help the California Department of Forestry and Fire Protection, better known as Cal Fire, get its people, equipment, and supplies to the front line by building a floating bridge across a river in Cache Creek Regional Park. As quickly as possible.

Before long, Ramirez was watching a truck called a common bridge transport slide a folded up pile of metal into the river, where it unfurled itself in two splashy steps, a piece of origami reverting to its original state. The suddenly flat slab of aluminum floated on the surface, held in place by ropes gripped fiercely by Ramirez’s soldiers. This was the first piece of the improved ribbon bridge the 132nd had come here to build, a Lego-like thing that would save California’s firefighters vital time in their efforts to contain the County Fire and provide them an escape route should they have to fall back.

The 132nd is just one of many military units around the country and planet trained to install this sort of floating, temporary bridge, meant to last a few weeks and move supplies and people when war or natural disaster nix standard engineering solutions. This variety of bridge—designed by General Dynamics European Land Systems—has bridged the Tigris and Euphrates rivers as American soldiers invaded Iraq in 2003, helped workers get cranes and oil booms into the Gulf of Mexico to contain the 2010 Deepwater Horizon oil spill, and stretched across Poland’s Vistula River during NATO’s training exercise, Exercise Anakonda, in 2016. And as Hurricane Florence continues to flood the mid-Atlantic, they’re being readied to move emergency personnel and relief supplies into the river-surrounded town of Georgetown, South Carolina.

Any improved ribbon bridge is made up of two types of bays, essentially big floating rectangles. The ramp bays, which have one sloped side, will connect to each shore. The interior bays go between them; their number depends on how long a bridge you’re making. Each is 22 feet long, weighs about 13,000 pounds, is made of aluminum, and floats the same way a pontoon does. Usually, the crew launches one of the ramps into the water first, using that common bridge transport, which backs up to the water and uses a crane arm to slide the payload off its flatbed. They usually angle this first piece of equipment upstream, so it’s out of the way as they drop the other bays into the water.

For easier transport on land, each bay is folded up like a W. Once on the water, it unfurls with a splash, and crew members in bridge-erection boats—essentially high-performance tugs—nudge it into position. Once two bays are lined up, the soldiers dash over to lock them in place. They start by using supersized hex wrenches to drop heavy-duty pins, 2 inches round, into a set of interlocking loops. Then they deploy the “dog bones,” the spring-loaded, dumbbell-shaped locks that span the two bays, fitting into a special groove. Meanwhile, the landlubbing crew members use cables to anchor the ramps, usually sinking them into the ground or tying them to trees. And that’s about it.

Uninstalling an improved ribbon bridge is about a simple as setting it up. Unlock the bays, push them to shore, and use that crane-wielding boat to winch them back to dry land, in the process folding them back into that W shape. Then put them away until the next time someone needs a bridge over troubling waters.