1. Fit barrel into chamber, making sure the muzzle knife is facing out.
2. Place muzzle knife over potato.
3. Apply pressure until potato shears into the barrel.
4. Use a rod to ram the potato into the barrel, stopping 1 inch from the chamber.
5. Open chamber and apply one squirt of aerosol hairspray. Close chamber.
6. Aim at target & flick ignitor until cannon fires.
7. If it doesnt fire on 2 or 3 flicks, open the chamber, let it breathe, close it and try again.
8. Troubleshooting: If your igniter isn't sparking, you may need to realign your flint roller (see below).        

NOTE: Increase or decrease propellent quantity to obtain desired results.
It takes a bit of practice to find your sweet spot.