1. A MOP HAVING A SLAB OF PLASTIC SPONGE MATERIAL, A RIGID BASE TO WHICH SAID SLAB IS FIXED IN TOTALLY UNDERLYING RELATION TO SAID BASE, SAID BASE HAVING MEANS IN FIXED ASSOCIATION THEREWITH DEFINING AN UPWARDLY FACING AREA COMMENSURATE WITH THE PERIPHERAL LIMITS OF SAID BASE, A PAIR OF RECESSES ALONG SPACED PARALLEL LINES ADJACENT OPPOSITE EDGE PORTIONS OF SAID AREA, SAID RECESSES FACING TOWARD PORTIONS OF SAID AREA BETWEEN SAID EDGE PORTIONS, A CARRIER PLATE INCLUDING A PAIR OF WINGS JOINED BY A HINGE, SAID WINGS PRESENTING EDGE PORTIONS REMOTE FROM AND PARALLEL TO SAID HINGE WHICH ARE RECEIVABLE IN SAID RECESSES WHEN SAID WINGS OF THE CARRIER PLATE ARE IN OUT-