To detonate the grenades, one needed only to generate an electric charge through the copper thread, which warmed up and detonated the explosive powder. The black powder has the characteristic of explosive combustion, when lighted in a closed space. A pressure thus builds up in the shell, causing it to rupture and the grenade explodes. It has been suggested that these devices have been used to blow up concrete shelters or underground dug-outs. Nevertheless, according to Adj. T. Wittouck, demolition squad of the Belgian Army (Poelkapelle), the charge of the devices wasn’t large enough to blow up heavy objects. He thinks these improvised grenades were used to take out smaller obstructions, such as barbed wire entanglements.