"Soon they will begin to fold space." -Leto Atreides I
Fold Space was Non-Einsteinian space through which a Heighliner moved in order to transit from one star system to another. Fold Space was accessed through the Heighliner's Fold Space engines, which could be activated in space or on the ground. They were one realization of Tio Holzmann's equations. A Guild Navigator was capable of selecting a path through the compleities of Fold Space, which maximized the probability of the Heighliner successfully transiting from origin to destination. The Fold Space engines, working under the guidance of the Navigator, took the Heighliner on its journey.