  Geometrical structures of confining surfaces profoundly influence the
adsorption of fluids upon approaching a critical point T_c in their bulk phase
diagram, i.e., for t=(T-T_c)/T_c -> +/-0. Guided by general scaling
considerations, we calculate, within mean-field theory, the temperature
dependence of the order parameter profile in a wedge with opening angle
gamma<pi and close to a ridge (gamma>pi) for T>T_c and T<T_c and in the
presence of surface fields. For a suitably defined reduced excess adsorption
Gamma_\pm(gamma,t -> +/-0)~Gamma_\pm(gamma)|t|^{beta-2nu} we compute the
universal amplitudes Gamma_\pm(gamma), which diverge as Gamma_\pm(gamma
->0)~1/gamma for small opening angles, vary linearly close to gamma=pi for
gamma<pi, and increase exponentially for gamma -> 2pi. There is evidence that,
within mean-field theory, the ratio Gamma_+(gamma)/Gamma_-(gamma) is
independent of gamma. We also discuss the critical Casimir torque acting on the
sides of the wedge as a function of the opening angle and temperature.
