A trajectory guide includes a guide body defining a selected trajectory through an entry aperture or opening, engagement surfaces for insertion into the entry aperture, and a fixing mechanism coupling the guide body with the engagement surfaces. The engagement surfaces may be easily fixed within an entry aperture and the guide body positioned in a selected orientation using the fixing mechanism to provide simple mounting of the trajectory guide. In some instances, the engagement surfaces may be fixed within the entry aperture and the guide body fixed in a selected orientation with a single fixation motion.