  We consider three-dimensional statistical systems at phase coexistence in the
half-volume with boundary conditions leading to the presence of an interface.
Working slightly below the critical temperature, where universal properties
emerge, we show how the problem can be studied analytically from first
principles, starting from the degrees of freedom (particle modes) of the bulk
field theory. After deriving the passage probability of the interface and the
order parameter profile in the regime in which the interface is not bound to
the wall, we show how the theory accounts at the fundamental level also for the
binding transition and its key parameter.
