Deckling is the term used in the paper industry to refer to the process of deciding how to cut enormous drums of paper into smaller reels. The equivalent problem in other industries is known as the cutting stock problem.

Whatever the industry, the basic problem is to decide how to cut a large rectangle into smaller ones. In the paper industry the fact that one is cutting rectangles is obscured by the disproportion of the rectangle's dimensions - its length may be 10,000 times its width - and the way in which the rectangles are rolled up along their lengths into cylinders. No such rolling-up is possible in glass-making, where the true nature of the problem is more obvious.

In all these industries the manufacture of the material has been made into a continuous process in which a web of fixed width is emitted continuously from one end of a giant machine. The physical properties of the material are different in the "machine-direction" (i.e. direction of flow) and the "cross-direction", so a sheet 1000 x 800 mm is not the same as a sheet 800 x 1000 mm. Different machinery is used to make cuts across the web ("chops") from that used to make cuts parallel to the direction of flow ("slits").

Economies of scale and the desire for higher quality lead to ever larger machines, but the ultimate size in which the material is consumed remains unchanged (humans aren't getting bigger very fast). This means that the cutting problems are becoming more complicated.

In some cases the customer demand is for standard sizes, e.g. A4 paper. In others there is enormous variability, e.g. packaging; window glass. Where customer demand is largely standard, the machines are built so that they can produce the standard sizes very efficiently, e.g. a machine to make office-grade paper may be 12 sheets wide. But where demand is for assorted sizes there is no obvious width for the machine. There is then a real problem in working out how to cut up the material to meet customers' demands. Material which is left over after cutting the sizes ordered by customers is waste. Although it can be recycled, this waste represents a substantial loss of value and it is highly desirable to minimize it.

Although there is a well-understood approach to solving cutting-stock problems, in practice there is little value in producing mathematically optimal solutions to the problem viewed in isolation. The deckling problem in a paper mill is part of the larger problem of planning and scheduling the mill. Deckling lies between manufacture and finishing and any reduction in trim-loss at deckling must not be at the expense of less efficient finishing or increased losses elsewhere.