  The interpretation of so-called cosmic string in black hole spacetimes has
settled down to an unsatisfactory state.
  In this article we try to provide a different model for these cosmic strings
by explicit construction of these spacetimes from the Bonnor rocket solution.
It is shown that the correct stress-energy tensor is that of null dust with a
rather strange energy density --- first derivative of Dirac delta distribution.
  We will discuss the Schwarzschild solution and the C--metric. In the latter
case we will show that there is a momentum flux through the cosmic string,
causing the acceleration of the black hole.
