  In metric measure spaces, we study boundary traces of BV functions in domains
equipped with a doubling measure and supporting a Poincar\'e inequality, but
possibly having a very large and irregular boundary. We show that the trace
exists in the ordinary sense in a certain part of the boundary, and that this
part is sufficient to determine the integrability of the rough trace, as well
as the possibility of zero extending the function to the whole space as a BV
function.
