The condition behind unfinished business: at a bar's extreme the auction did not fully resolve because one side never transacted at the next tick beyond it. At a high, the market was bid but no aggressive buyer lifted the offer one tick above; at a low, the offer was hit but no aggressive seller hit the bid one tick below. The market tends to probe back to the level — and through it — to give the missing side a chance to transact and complete the auction.