The following three classes
of models of rigid submanifolds of higher type with CR dimension one are discussed:
1) A tube-like model that only depends on the real part of the holomorphic tangent
coordinate; 2) a radial model that depends on the modulus of the holomorphic
tangent coordinate and 3) a free model. The first and third models have a Lie group
structure which is analyzed. A characterization of the hull of holomorphy of the first
two models is presented along with a partial result on the hull of holomorphy of the
third.