An engineless rake or puffer is one which does not contain a specific engine for its operation. Instead it depends on perturbations of gliders or other objects by passing spaceships. The period of such objects is often adjustable, and in some cases the speed as well. An early example was the creation of c/5 rakes in September 1997, using gliders circulating among a convoy of c/5 spaceships. More recently, the passing spaceships themselves are also constructed, as in the Caterloopillar.