Definition
The quantity line at which a replenishment signal must be issued, equal to daily usage times lead time plus safety stock; a kanban card, an empty bin or a line painted on a rack are all physical forms of it.
In detail
The reorder point turns when to order into a visible position instead of a judgement someone has to make — which is exactly the dividing line between kanban and computer scheduling. All three of its inputs move: daily usage with demand, lead time with supplier performance, safety stock with variation, so it needs a recalculation rhythm rather than being set once for three years. On the floor it can be a card, an empty slot or an arrow painted on a rack; the form does not matter, what matters is that anyone walking past can tell whether it is time to replenish.
Example in practice
A part with daily usage of 20 pieces, a 5 day lead time and no safety stock gets a reorder point of 100 pieces, implemented as a kanban card at the bottom of the second bin. When the bin empties the card is pulled and receiving replenishes, so nobody counts stock daily any more.