  We verify the Kosterlitz Thouless scenario for three different SOS
(solid-on-solid) models, including the dual transforms of XY-models with
Villain and with cosine action. The method is based on a matching of the
renormalization group (RG) flow of the candidate models with the flow of a bona
fide KT model, the exactly solvable BCSOS model. We obtain high precision
estimates for the critical couplings and other non-universal quantities.
