The Block attribute is used for large volume option orders on ISE that consist of at least 50 contracts. To execute large-volume orders over time without moving the market, use the TWS Accumulate/Distribute trading tool.
You want to buy 10,000 XYZ option contracts for the best possible price. You select the XYZ option ticker line, then open the Order Ticket. In the Exchange field, you select ISE, then in the Price field you enter a limit price. Next you click the Miscellaneous tab and click the Block Order checkbox. This ensures that your order is made public and may result in a price improvement. You click Transmit to submit your order, or Accept to display the order on the trading screen before you submit it.
Any stock or option symbols displayed are for illustrative purposes only and are not intended to portray a recommendation.