An employee was sorting large parcels in the large parcel sorting area. The employee moved a gaylord box filled with parcels with a manual pallet jack. The employee was on the front side of the box, pulling down on the upper edge of the cardboard and tipping it over. As she stepped back and was pulling down, her feet slipped out from under her and she fell backward. As she fell, she placed both hands back to catch herself and fractured both wrists.