Carton sizers, also known as carton reducers, add new perforations for folding a box to the exact size required for the items being shipped. This reduces the need for void fill and helps save on shipping costs. Sizers are ruled for precise measuring and include a hook for attaching to the lip of a box. Once the desired perforation line depth has been determined, the sizer is moved around the inside of the box to create the new scoreline. A box cutter is used to cut the corners of the box to create new flaps for folding.