Lock

FIG. 1 is a front elevational view of a lock, showing our new design; FIG. 2 is a rear elevational view thereof; FIG. 3 is a left side view thereof; FIG. 4 is a top plan view thereof; FIG. 5 is a front, top and right side perspective view thereof; FIG. 6 is a perspective view of the lock thereof, shown in an alternative configuration of use; FIG. 7 is a perspective view of the lock thereof, shown in an alternative configuration of use; and, FIG. 8 is a bottom plan view thereof of the lock thereof. The broken lines shown in FIG. 7 depict environmental subject matter only and form no part of the claimed design. The broken lines and portions within the broken lines shown in FIG. 2 depict portions of the lock that form no part of the claimed design.