A lattice-based model of the confinement of homopolymer free chains between two flat solid surfaces, each covered with end-tethered flexible chains, is developed. The free energy and free energy change for the formation of the confined state from reference states of the different components are calculated based on lattice and scaling theory concepts. Entropic and energetic factors determine the free energy of the system. The dependency of free energy and free energy change on the chain lengths (molecular weights) of free polymers and tethered polymers, the density of end-tethered chains on the surfaces, the distance between the surfaces, and the various intersegment interaction energy parameters for various component species, were studied. The phase diagrams obtained in this work provide ways for designing thermodynamically stable systems in various regimes. The results are qualitatively in agreement with those from earlier models based on self-consistent field theory and experiments. Copyright © 2012 Taylor and Francis Group, LLC.