The Yaphit Pass was a stable wormhole between Etrusca and Thule. As Thule lay some distance above the galactic plane, projection drive would not provide access to the distant planet. The Yaphit Pass provided the only stable passage to Thule.
Some time before 432, the Metis government discovered that the wormhole did not completely collapse but left a remnant. Though dangerous, a ship could navigate it. In 432, as Metis, Amargosa, and Farigha seceded from the Compact, the new Metisian Navy sent the Bova to carry Jayne Best to Thule for treatment of her injuries.