a method for permanently compacting a hollow resilient structure such as a recyclable plastic container to facilitate recycling thereof . as the structure is compressed cutting blades provided on the compressing surface perforate the walls of the container thereby cutting interlocking tabs into the surface . at the same time the interlocking tabs are forced outward and through the cavity left in the walls of the container by displacement of the tabs . the tabs straddle the cavity and become locked against the walls of the container by the separating force of the resilient plastic .