Plant and mining supply
Steel, power and mining operations bring contractors working to audited terms with purchase orders, gate registers and specifications. Grade and size on the item mean the invoice states exactly what was supplied, which is what a later query is settled from.
Size-wise rebar and sections
A contractor asks whether you have four tons of one particular size, which is only answerable if each size is its own item with its own stock and rate. That structure also makes the reorder list readable rather than a guess.
Money that moves with the rolling mills
Payment here follows the buyer own realisation rather than any agreed date, so a slow quarter in steel reaches the material shop a few weeks later as a run of unpaid accounts. Watching the age of each balance rather than the total is what buys you those few weeks of warning, and a limit per contractor decides how much of that slow quarter the shop ends up carrying.