  The gap between two component debris disks is often taken to be carved by
intervening planets scattering away the remnant planetesimals. We employ N-body
simulations to determine how the time needed to clear the gap depends on the
location of the gap and the mass of the planets. We invert this relation, and
provide an equation for the minimum planet mass, and another for the expected
number of such planets, that must be present to produce an observed gap for a
star of a given age. We show how this can be combined with upper limits on the
planetary system from direct imaging non-detections (such as with GPI or
SPHERE) to produce approximate knowledge of the planetary system.
