Write down what you ran out of, and when. That is the whole tool. After a month or two the pattern shows up on its own, and the items that keep coming back are the ones whose reorder points are too low.
A reorder point is just the number that says order now, worked out from how fast an item moves and how long your supplier takes. StockSolve calculates it for every item you carry.
Run the free auditThis log is saved in your browser only. Nothing is uploaded, and clearing your browser data clears it.