  We exploit the intrinsic difference between disordered and crystalline solids
to create systems with unusual and exquisitely tuned mechanical properties. To
demonstrate the power of this approach, we design materials that are either
virtually incompressible or completely auxetic. Disordered networks can be
efficiently driven to these extreme limits by removing a very small fraction of
bonds via a selected-bond removal procedure that is both simple and
experimentally relevant. The procedure relies on the nearly complete absence of
any correlation between the contributions of an individual bond to different
elastic moduli. A new principle unique to disordered solids underlies this lack
of correlation: independence of bond-level response.
