  We present the solution of a linear Restricted Solid--on--Solid (RSOS) model
in a field. Aside from the origins of this model in the context of describing
the phase boundary in a magnet, interest also comes from more recent work on
the steady state of non-equilibrium models of molecular motors. While similar
to a previously solved (non-restricted) SOS model in its physical behaviour,
mathematically the solution is more complex. Involving basic hypergeometric
functions ${}_3\phi_2$, it introduces a new form of solution to the lexicon of
directed lattice path generating functions.
