Protein combinatorial libraries have become a platform technology for exploring protein sequence space for novel molecules for use in research, synthetic biology, biotechnology, and medicine. To expedite the isolation of proteins with novel/desired functions using screens and selections, high-quality approaches that generate protein libraries rich in folded and soluble structures are desirable for this goal. The binary patterning approach is a protein library design method that incorporates elements of both rational design and combinatorial diversity to specify the arrangement of polar and nonpolar amino acid residues in the context of a desired, folded tertiary structure template. An overview of the considerations necessary to design and construct binary patterned libraries of de novo and natural proteins is presented.