  Spectral properties and the confinement phenomenon for the coupling $H+V$ are
studied, where $H=-i\alpha\cdot\nabla +m\beta$ is the free Dirac operator in
$\mathcal{R}^3$ and $V$ is a measure-valued potential. The potentials $V$ under
consideration are given in terms of surface measures on the boundary of bounded
regular domains in $\mathcal{R}^3$.
  A criterion for the existence of point spectrum is given, with applications
to electrostatic shell potentials. In the case of the sphere, an uncertainty
principle is developed and its relation with some eigenvectors of the coupling
is shown.
  Furthermore, a criterion for generating confinement is given. As an
application, some known results about confinement on the sphere for
electrostatic plus Lorentz scalar shell potentials are generalized to regular
surfaces.
