Complex sentence: The Kearny Fallout Meter or KFM is an expedient radiation meter designed to be able to be constructed immediately before or during a nuclear attack by someone with a normal mechanical ability and from common household items.
Split into simpler sentences: The Kearny Fallout Meter or KFM is an expedient radiation meter. It is designed such that someone with a normal mechanical ability would be able to construct it before or during a nuclear attack and from common household items.