We use several parts in our designs that are purchased as full length items, like DIN rail, extruded wireways and such. Each of these items is brought in under our part number in ERP and allocated on a "as required" basis, then the shop takes, for instance, a 2 meter long part, cuts it down to what they require, and returns the rest to stock. In CAD, we have typically added configurations to each of these models for every length that is required at the time, or perhaps isnt needed sometimes,