  Recently, new insights in the relation between the geometry of the vessel
that confines a fluid and its thermodynamic properties were traced through the
study of cluster integrals for inhomogeneous fluids. In this work I analyze the
thermodynamic properties of fluids confined in wedges or by edges, emphasizing
on the question of the region to which these properties refer. In this context,
the relations between the line-thermodynamic properties referred to different
regions are derived as analytic functions of the dihedral angle $\alpha$ , for
$0<\alpha<2\pi$ , which enables a unified approach to both edges and wedges. As
a simple application of these results, I analyze the properties of the confined
gas in the low-density regime. Finally, using recent analytic results for the
second cluster integral of the confined hard sphere fluid, the low density
behavior of the line thermodynamic properties is analytically studied up to
order two in the density for $0<\alpha<2\pi$ and by adopting different
reference regions.
