Patterning of micro- and nanometer scale structures by means of nanostencils (shadow masks) is increasingly being used as a simple, clean and low-cost alternative to photolithography. It can be shown, that sub-100-nm scale features can be fabricated through 100-nm thick membranes. Currently, large area pattern transfer using nanostencil lithography is limited by the mechanical stability of the shadow-mask membrane itself. The reason is that the deposited material induces undesirable stress in the membrane causing excessive bending or breakage and consequent loss in dimensional control. In this contribution, a remedy for the fabrication and application of nanostencils that are suitable for the creation of high-density nanopatterns on large surface areas is presented. The improved nanostencils incorporate in-situ, local stabilization structures increasing their moment of inertia, I, which is the structural property directly related to deformability.