With Lai-Sang Young, I considered a heat conduction model which is an open system in which particles exchange momentum with a row of (fixed) scatterers without recoil. The main phenomenon for this model is freezing, which is the slowing down of particles with time although there is no dissipation. Most results evade rigorous mathematical analysis, but several features shed light on the intriguingly slow convergence to a steady state in which all but one particle remain active.