A picture depicting the trapping set for exit I. The shaded area in region A is the set of initial conditions that starts from disk 1 and leaves directly through exit I with no additional collisions within the scattering region, while the shaded area in region B is the set that starts from disk 2 and immediately leaves through exit I, and the shaded area in region C is the set that starts from disk 3 and immediately leaves through exit I.