Bid once, bid true.
Open lots: your bid is public, must beat the best by the posted step, and funds the moment you place it. Sealed lots: the chain records a commitment and your public ceiling — never your price. Both bind instantly. There is no cancel button because there is no cancel action. It doesn’t exist in the grammar.
Open lots extend the clock on last-minute bids — sniping earns you a longer fight, not a steal. Sealed lots can’t be sniped at all: there’s nothing visible to snipe.