My bad. The fire tube is also known as the fire piston. Basically its just that, a two piece unit wich uses the diesel principle to ignite a piece of punkwood or "Char" (this is not charcol).
The piston part has a cupped end in wich the flammable is placed it is then inserted into the tube and given two sharp raps. The increase in pressure causes the temp to rise igniting the flammable and letting you start you'r tinder.
If you can find them a Fresnel lens from an overhead projector is a real firestarter. O a sunny day it will start a fire in seconds and you can focus the beam to a pinpiont that will cut through a soda can.
It goes without saying they will incinerate flesh!! Be careful.