Fuse, burst charge, propellant, priming, lift charges, etc. etc. It pays to spend some time trying to make a good quality of black powder. Having good black powder makes the construction of a lot of things easier. Fuse , indispensible, ofcourse. For providing a delay, for connecting things together etc.
Fuse exists in many varieties with different properties.
Commercial fuse is usually more reliable than homemade fuse, but for some purposes the reduced reliability is not really a problem. Paper tubes are commonly used for casings. Tubes can be found in many places. They can also be bought, and ofcourse, you can roll your own. A technique that takes some practice to do well, but can be very usefull.