a block molded from a polymeric material has a through passageway to contain a percussive shock wave . angularly related channels communicate with the containment passageway for receiving arcuate segments of detonation cord . alignment of a plurality of blocks provides a convenient packaging setup for the cord . a percussive signal traveling along the cord can be short - circuited in the packaging setup . a diode version of the block can react to the signal in a given direction of travel .