In dealing with this question I have chosen to focus more on the SME (Small to Medium Enterprise). The reason being, there are plenty of off the shelf software packages and established companies who can help you with the installation of a SCM system. Building your own supply chain requires that you know exactly where you sit in the over transition of the product that you are either selling, making or distributing. Once this has been established you are then in a position to start building the supply chain and then managing it. Every item moved, touched or transformed within the supply chain has to at some point rely on external parties to make a change to the item. this can be as simple as re-packaging an item to the more complex actions associated with customs clearance and shipping to overseas clients. the building blocks of the supply chain will required you to understand the movement of goods before and after you handle it, once you know where your goods are coming from and where they are going to then you start to put times (days, hours, weeks) against this part of the supply chain. Then the basics of supply and demand as we as peaks in market trends. for instance the build up to Christmas has caught out many companies who did not plan far enough ahead to make sure that their supply chain was robust enough to handle not only the inbounding of materials but also the outbounding of finished goods.