  We study open and unoriented strings in a Topological Membrane (TM) theory
through orbifolds of the bulk 3D space. This is achieved by gauging discrete
symmetries of the theory. Open and unoriented strings can be obtained from all
possible realizations of $C$, $P$ and $T$ symmetries. The important role of $C$
symmetry to distinguish between Dirichlet and Neumman boundary conditions is
discussed in detail.
