Assault on HYDRA Headquarters
After Captain America distracted the Red Skull by infiltrating HYDRA headquarters in the Alps, members of the Howling Commandos used Zip-line Guns to zip-line into the base from the adjacent mountain, storming the base through its window.
Antoine Triplett retrieved his grandfather's Howling Commando gear and offered it to Phil Coulson as a tactical advantage during the undercover investigation on Cybertek and the missions to come. The Zip-line Gun was among these items.
Triplett later used his grandfather's Zip-line Gun to create an escape route for Phil Coulson and Melinda May when they performed an undercover infiltration mission within Cybertek Corporate Headquarters.
Similar to a modern spear-gun, a Zip-line Gun is a gun-like device that launches a spear-like metal bar with an attached zip-line to set up a zip-line path for transportation. The gun is designed to launch its spear with enough force to embed it in a surface at a variable distance and properly anchor its end of the zip-line. After firing, the zip-line unravels from a spool below the barrel of the gun. The spear and gun ends of the zip-line can then be properly anchored to allow transportation from a higher area to a lower base level or across a large open space.