From the start, John Leeming's reconnaissance mission into enemy territory was doomed to be a one-way trip. But when he crashed on a distant planet and was captured by aliens, he found that his sense of self-preservation would not accept defeat. So he began a complex scheme to confound his captors--and to terrify them. All he had to work with was a block of wood and a length of copper(and a cooperative but imaginary friend he called Eustace.)
From the book: "Whenever Man had found himself unable to master his environment with his bare hands the said environment had been coerced or bullied into submission by Man plus X. That had been so since the beginning of time; Man plus a tool or a weapon. But X did not have to be anything concrete or solid. It did not have to be lethal or even visible. It could be as intangible and unprovable as the threat of hellfire or the promise of heaven. It could be a dream, an illusion, a whacking great thundering lie--just anything. There was only one positive test: wether it worked."
Keith Laumer's Retif would have loved working with John Leemer!