[Bozos of Bones]

As for the singularity having double black holes as it's sides, that doesn't have to be. If a black hole should open a singularity through space-time, with an exit on the ofher side, then one of the following should, theoretically, occur: Both ends are negative black holes(suction)
OR
Both ends are positive black holes(sometimes known as white holes, these theoretical objects are not really white. They are an inverse of a black hole, having the same strenght of force, but in the opposite direction, pushing things away.)
OR
The polarisation effect occurs, and one end is a positive and the other is a negative black hole. This, theoreticians say, is the most likely occurence.
OR
The black hole is fed up, it's mass becomes infinite and it is swallowed into space-time or, a bit more Sci-fi, subspace. The same happens in a white hole. It's mass becomes null and void, it ceaces to exist. The singularities lose their ancor points and they become instable, shifting tunnels.