From publisher blurb:
Grenadiers are individuals wholly devoted to explosions and destruction. They spend their days designing and crafting grenades of different types, with the overall goal of designing a grenade generally more destructive. Grenadiers are former soldiers, from where they got their first taste of explosives and grenades.
Having left the military, they were unable to also leave behind their taste for destruction. They soon acquire or build a Grenade Kit, and the rest is explosive. In the modern era, with vaporizers and plasma rays, there isn't much use for demolitions experts outside of the military—except out on the frontier planets, that is, where someone who can blow up stuff real damn good never goes out of style.