  Kruskal's extension solves the problem of the arrow of time of the
``Schwarzschild solution'' through combining two Hilbert manifolds by a
singular coordinate transformation. We discuss the implications for the
singularity problem and the definition of the mass point.
  The analogy set by Rindler between the Kruskal metric and the Minkowski
spacetime is investigated anew. The question is answered, whether this analogy
is limited to a similarity of the chosen "Bildr\"aume'', or can be given a
deeper, intrinsic meaning. The conclusion is reached by observing a usually
neglected difference: the left and right quadrants of Kruskal's metric are
endowed with worldlines of absolute rest, uniquely defined through each event
by the manifold itself, while such worldlines obviously do not exist in the
Minkowski spacetime.
