Fastener

FIG. 1 is a perspective view of fastener, showing the new design; FIG. 2 is a front view thereof; FIG. 3 is rear view thereof; FIG. 4 is a left-side view thereof; FIG. 5 is a right-side view thereof; FIG. 6 is a top view thereof; FIG. 7 is a bottom view thereof; and, FIG. 8 is a perspective view thereof, shown in an environment of use. The broken lines represent environmental structure and form no part of the claimed design.