The ability of geckos to adhere to vertical solid surfaces comes from their remarkable feet with millions of projections terminating in nanometer spatulae. In this paper, we present a simple yet robust method for fabricating directionally sensitive dry adhesives. By using electrospun nylon 6 nanofiber arrays, we create gecko-inspired dry adhesives, that are electrically insulating, and that show shear adhesion strength of 27 N/cm2 on a glass slide. This measured value is 270% that reported of gecko feet and 97-fold above normal adhesion strength of the same arrays. The data indicate a strong shear binding-on and easy normal lifting-off. Size and surface boundary of fibers both affect on the shear adhesion. This anisotropic strength distribution is attributed to enhanced shear adhesion strength with decreasing fiber diameter and an optimum performance of nanofiber arrays in the shear direction over a specific range of thicknesses.