  The effects of columnar pins on the flux lines in a model High-Tc
superconductor in an applied field are studied through Monte Carlo simulations.
An analytic solution for a single line case is obtained and compared with the
simulation results. By introducing a tilted potential, we study simulated ``IV"
characteristics and the results indicate a distinct scaling behavior above and
below the depinning temperature. We introduce a diverging length scale measured
in terms of a ``retrapping length'' to analyze self-similar behavior across the
depinning transition.
