  In the paper we derive rational solutions for the lattice potential modified
Korteweg-de Vries equation, and Q2, Q1($\delta$), H3($\delta$), H2 and H1 in
the Adler-Bobenko-Suris list. B\"acklund transformations between these lattice
equations are used. All these rational solutions are related to a unified
$\tau$ function in Casoratian form which obeys a bilinear superposition
formula.
