  In the paper, the basic results on boundary trace of the book "Sobolev
spaces" by V. Maz'ya are generalized to a wider class of regions. In the book,
boundary trace of BV-functions is defined for regions with finite perimeter and
the main results were obtained under the assumption that normals in the sense
of Federer exist almost everywhere on the boundary. Instead of that, we
investigate trace of BV functions on any countably (n-1)-rectifiable set.
