The team members of the Engine Company are charged with one, big job: douse a fire with water as quickly as possible. Be it from outside the building, inside with the flames, or from high atop a truck-mounted “bucket” their hoses blast powerful jets of water right into the heart of the fire.
 

nozzle
Nozzle
  At the scene of a fire the first job of the firefighter in the Nozzle position is to ensure the nozzle is hooked up to the first length of hose. When the team is in place, the Nozzle position advances the hose into the burning building.
backup
Backup
  When the water is turned on, the hose is very heavy and difficult to control. The Backup Firefighter is positioned like a human brace behind the shoulder of the firefighter in the Nozzle position. The Backup firefighter becomes the main "push" of the hose line and helps to alleviate most of the weight and pressure for the Nozzle firefighter.