The chum detonator is a combination of chum and a simple bar of white soap. It also has wires going through it. The chum acts as an explosive material, while the soap acts as a timer device to initialize the explosion.
Role in episode
The chum detonator is used by Plankton to blow apart a wall in the Bikini Bottom Jail. His plan succeeds, but the prison guards cover up the large hole with their bodies. However, they get stuck in place and Plankton and his cellmates go out through the front door.