  A long skinny gate across a fractional quantum Hall fluid at filling
$\nu=1/m$ with odd integer $m$, creates a novel one-dimensional (1d) system
which is isomorphic to a disordered 1d electron gas with {\it attractive}
interactions. By varying the gate potential along such a line junction, it
should be possible to tune through the 1d localization transition, predicted
for an attractively interacting electron gas. The key signature of this 1d
metal-insulator transition is the temperature dependence of the conductivity,
which diverges as a power of temperature in the metallic phase, and vanishes
rapidly in the insulator. We show that the 1d conductivity can be extracted
from a standard Hall transport measurement, in the regime where the Hall
conductance is close to its quantized value. A line junction in a $\nu=2/3$
quantized Hall fluid is predicted to exhibit a similar localization transition.
