  We investigate the interplay between confinement and the fermion doubling
problem in Dirac-like Hamiltonians. Individually, both features are well known.
First, simple electrostatic gates do not confine electrons due to the Klein
tunneling. Second, a typical lattice discretization of the first-order
derivative $k \rightarrow -i\partial_x$ skips the central point and allow
spurious low-energy, highly oscillating solutions known as fermion doublers.
While a no-go theorem states that the doublers cannot be eliminated without
artificially breaking a symmetry, here we show that the symmetry broken by the
Wilson's mass approach is equivalent to the enforcement of hard-wall boundary
conditions, thus making the no-go theorem irrelevant when confinement is
foreseen. We illustrate our arguments by calculating the following: (i) the
band structure and transport properties across thin films of the topological
insulator Bi$_2$Se$_3$, for which we use ab-initio density functional theory
calculations to justify the model; and (ii) the band structure of zigzag
graphene nanoribbons.
