  In Phys. Rev. Lett. 96, 035702 (2006) we introduced a class of kinetically
constrained models which display a dynamical glass transition. We focused on a
particular example: the "knights" model. As correctly pointed out by Jeng and
Schwarz cond-mat/0612484, we overlooked some additional directed frozen
structures of the knights model which are not simple directed percolation (DP)
paths: these "thicker" directed structures lower the critical density. Here we
argue that, nevertheless, the full directed processes are in the DP
universality class and the T-junctions between perpendicular segments of these
give rise to a jamming percolation transition with the universal properties
discussed in our previous work. Moreover, we present other models for which all
our previous results, included the value of the critical density, hold
rigorously.
