  The gauge principle is fundamental in formulating the Standard Model.
Fermion--gauge-boson couplings are the inescapable consequence and the primary
determining factor for observable phenomena. Vertices describing such couplings
are simple in perturbation theory and yet the existence of strong-interaction
bound-states guarantees that many phenomena within the Model are
nonperturbative. It is therefore crucial to understand how dynamics dresses the
vertices and thereby fundamentally alters the appearance of
fermion--gauge-boson interactions. We consider the coupling of a
dressed-fermion to an Abelian gauge boson, and describe a unified treatment and
solution of the familiar longitudinal Ward-Green-Takahashi identity and its
less well known transverse counterparts. Novel consequences for the
dressed-fermion--gauge-boson vertex are exposed.
