  We present realistic models of flavor in SU(5) and SO(10) grand unified
theories (GUTs). The models are renormalizable and do not require any exotic
representations in order to accommodate the necessary GUT breaking effects in
the Yukawa couplings. They are based on a simple clockwork Lagrangian whose
structure is enforced with just two (one) vectorlike U(1) symmetries in the
case of SU(5) and SO(10) respectively. The inter-generational hierarchies arise
spontaneously from products of matrices with order one random entries.
