We investigate an annealed hard sphere fluid in contact with a rigid, random fiber network modeled by quenched, vanishingly thin hard needles. For this model a quenched-annealed density functional theory is presented that treats arbitrary spatially inhomogeneous situations, in particular anisotropic and spatially varying needle distributions. As a test case we consider the structure of the hard sphere fluid at the surface of an isotropic fiber network and find good agreement of the theoretical density profiles with our computer simulation results. For high needle densities the surface acts like a rough impenetrable wall. In the limit of infinite needle density the behavior near a smooth hard wall is recovered. Results for the partition coefficient agree well with existing data. (C) 2003 American Institute of Physics.