The extend toggle enables you to create a skew curve from currently-trading
option expirations and automatically apply the skew curve to new, far-out option
expirations as they begin to trade. For example, if the fifth-out-month
options have not begun trading yet, you can create a skew based on the
fourth-out-month options and apply it to the fifth-month options when they begin to trade
using the extend toggle.
The Extend Toggle