I am trying to get cardboard piece off back of whirlpool refrigerator, screws holding it on are too tight. Need to get it off to remove drip tray full on water.

Use a 1/4" nut driver, but make sure to clean the coils and fan blades while you have it off and replace it before running unit because many will not draw air through coils without cover on the back. Use spray soap and a water hose nozzle to clean the coils properly and unplug before removing back cover.