A detonating device is a device used to set off an explosive. It typically consists of a petard, which is a small explosive device, and a CAP, which is a small metal cylinder filled with a detonating material. The petard and the CAP are connected by a fuse, and when the fuse is lit, it causes the CAP to ignite and set off the petard. The caps can also be used in conjunction with other explosives, such as dynamite, to create larger explosions.