As its name implies, the signature use of parachute cord is in holding together the various components of a parachute. The tensile strength of parachute cord comes from its dual construction. The interior of the cord is composed of seven two-ply nylon fibers woven into a central core. A braided sheath of stronger nylon (32 strands) then goes over that interior, providing an average strength of 550 pounds per square inch for the most commonly used variety — hence the popular name, "550 cord."
The term "rip cord" can be a bit misleading, however, since parachute cord figures only in a small loop that pulls a lever to start the process of releasing the chute. One often overlooked quality of parachute cord is that when the outer sheath is cut away, the inner fiber can be used for such things as fishing line or shoe laces. As such, parachute cord is often included in the backpacks of wilderness hikers.
Given this versatility, the use of parachute cord soon spread from airborne units into other areas of the military. After World War II, it was introduced to the world at large through military surplus stores and took on a myriad of other uses — basically, anything that requires binding one object to another. Now, it is omnipresent as a commercial commodity.
Parachute cord received international publicity in February 1997 when it was used by Discovery astronauts to repair the Hubble Telescope. In places where the insulation had been worn away, Teflon® patches were applied and secured with parachute cord. Many American military units overseas have fashioned parachute cord into bracelets denoting their unit and geographical area of deployment. This reflects both the comfortable texture of the nylon rope and its place as a military icon.
Parachute cord does, however, have its limitations. Rock climbers and mountaineers are warned against using it, since the 550 (or, at peak, 700)pound strength can be misleading. The strength required to stop a human body in free fall is actually far more than that. Also, parachute cord is prone to abrasion when rubbed repeatedly over sharp, hard services such as rocks.