Final answer:
An implosion-type bomb is a device that makes instantaneous forced-entry fastenings into construction material by using shaped explosives to compress a sphere of fissile material, allowing a chain reaction to occur.
Step-by-step explanation:
The device described in the question is an implosion-type bomb, which is used for instantaneous forced-entry fastenings into construction material. It consists of a sphere of fissile material surrounded by shaped explosives. When the explosives are detonated simultaneously, the resulting shock wave compresses the fissile material, allowing the chain reaction to occur. This type of bomb requires much less fissile material and is more efficient, but also technically challenging.