  A general scheme has been proposed to study the critical behaviour of
integrable interaction-round-a-face models with fixed boundary conditions. It
has been shown that the boundary crossing symmetry plays an important role in
determining the surface free energy. The surface specific heat exponent can
thus be obtained without explicitly solving the reflection equations for the
boundary face weights. For the restricted SOS $L$-state models of Andrews,
Baxter and Forrester the surface specific heat exponent is found to be
$\alpha_s=2-(L+1)/4$.
