  We study bounded trace maps on hypersurfaces for Sobolev spaces from a point
of view that is fundamentally different from the one in the classical theory.
This allows us to construct bounded trace maps under weak regularity
assumptions on the hypersurfaces. In the case of bounded domains in $\mathbf
R^n$ we only require the continuity of the boundary. For hypersurfaces in the
whole space $\mathbf R^n$ we only assume that the hypersurfaces are Lebesgue
measurable. As an application of our trace maps we consider the Dirichlet
problem and we prove a coarea formula where the level sets are only assumed to
be Lebesgue measurable hypersurfaces.
