  We calculate critical couplings and string tensions in SU(2) and SU(3) pure
lattice gauge theory by a simple and inexpensive technique of two-lattice
matching of RG block transformations. The transformations are potential moving
decimations generating plaquette actions with large number of group characters
and exhibit rapid approach to a unique renormalized trajectory. Fixing the
critical coupling $\beta_c(N_\tau)$ at one value of temporal lattice length
$N_\tau$ by MC simulation, the critical couplings for any other value of
$N_\tau$ are then obtained by lattice matching of the block decimations. We
obtain $\beta_c(N_\tau)$ values over the range $N_\tau = 3 - 32$ and find
agreement with MC simulation results to within a few percent in all cases. A
similar procedure allows the calculation of string tensions with similarly good
agreement with MC data.
