You are familiar with the types and uses of explosives and can place them in such a way that the explosion will accomplish your goals. You can handle nearly any type of explosive, ranging from nitroglycerin and TNT to black powder, napalm and plastic.
Fireworks. You can blow up things. Sometimes without even injuring yourself. You are competent in what you do, sometimes using custom materials. You're a real pro, a terorrist extraordinaire. Hee hee. Boom! There goes the White House.