In this note investigations are
made of the problem of deciding if a given codimension one submanifold M is locally
flat in the ambient manifold N. The principal result is that if M has a locally
flat triangulation in which each closed simplex is locally flat in N, then M
is locally flat in N. This allows one to establish for simplicial homotopy
manifolds certain local flatness criteria that had been previously known for PL
manifolds.