Skylab carried three CMGs, mounted with their casings (and therefore their rotor axes when the gimbals were set to zero) facing in three mutually perpendicular directions. This ensured that the six 'polar blind spots' were spaced 90 degrees apart from each other. The 45 degree zero offset then ensured that the three 'blind strips' of the outer gimbals would pass halfway between neighbouring 'polar blind spots' and at a maximum distance from each other. The whole arrangement ensured that the 'blind areas' of the three CMGs never overlapped, and thus that at least two of the three rotor spins could be pointed in any given direction.