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.
The Reference Table to the upper right provides a general summary of the order type characteristics. The checked features are applicable in some combination, but do not necessarily work in conjunction with all other checked features. For example, if Options and Stocks, US and Non-US, and Smart and Directed are all checked, it does not follow that all US and Non-US Smart and direct-routed stocks support the order type. It may be the case that only Smart-routed US Stocks, direct-routed Non-US stocks and Smart-routed US Options are supported.
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.