All knives, whether circular or straight, must be kept keenly sharpened in order to produce clean edges. Soft cards and papers give more trouble than moderately hard stock when cutting in a guillotine. Some materials should be cut by the rotary cutter when exact measurements are essential, for although it may take longer, for index cards all supplies must be trimmed exactly to the same dimensions, and the very hard index boards are liable to be cut irregularly by the guillotine.
When sheets are ruled or printed, and are afterwards to be bound, the printed or ruled horizontal lines should coincide with the machine direction, or, as it is sometimes expressed, should run with the grain of the paper. The stitching and the binding which secure the leaves will then be fully operative, whereas if the paper is held with the back of the book parallel to the machine direction, the leaves are more liable to break away from the binding.
