It has been shown by Hilden
and Montesinos independently that any closed oriented 3-manifold M is a 3-fold
irregular branched covering of S3, p : M → S3. The purpose of this paper is to show
that the branch covering space map can be chosen in such a way that the set of
points at which p fails to be a local homeomorphism is the boundary of a disc in M.
One application of this result is a new proof that a closed oriented 3-manifold is
parallelizable.