Cardboard Closure

FIG. 1 is a top-right perspective view of a cardboard closure in accordance with my new design; FIG. 2 is a top plan view thereof; FIG. 3 is a bottom plan view thereof; FIG. 4 is a right-side elevational view thereof; FIG. 5 is a left-side elevational view thereof; FIG. 6 is a front elevational view thereof; and, FIG. 7 is a rear elevational view thereof. The broken lines depict portions of the article that form no part of the claimed design.