In the past, there was no remote computer-assisted transaction. All customers place orders by filling in written instructions (of course, they can also declare by telephone) and submitting them to the room of the futures company (where the quotation is made), and then the staff in the room will report to the place where the exchange is located by telephone. This staff member is called "customs broker" and "order clerk".
When your order is closed, there will be a return on the seat, and then the broker will inform you of the closing result. If you want to cancel the order, you should also inform the seat room to operate.