  We describe time-dependent tunneling of massless particles in 1+1 dimensional
string field theory. Polchinski's description of the classical solutions in
terms of the Fermi sea is used to identify the leading instanton contribution
connecting the two half-lines. The field theory lagrangian is proportional to
$1/g^2$, where $g$ is the string coupling constant, but the $S$-matrix for
tunneling from one half-line to the other behaves as $\exp(-C/g)$. We note the
constant~$C$ involves curious boundary contributions and observe that a
prescription connecting the two half-lines unifies treatments of the Fermi
level above and below the barrier. We also note the relation to recent work of
Brustein and Ovrut.
