Terrorists and criminal bombers sometimes use open or “straight” bombs consisting of a completely unconcealed high explosive charge and a delay initiating system. The device is simple, open and obvious for what it is.
However, more often they go to some length to conceal IEDs, making them more difficult to discover and deal with. The main charge explosive, power source, detonator and initiating system (and hidden boobytrap devices) are all concealed and disguised to make them look innocent to the casual observer, intended victim, or first responder.
Securesearch has become a master at concealing IED training aids inside assorted containers.