The toolbar for forward and yield curves contains these buttons:
Forward button
This button changes a yield curve to a forward curve.
Yield button
This button changes a forward curve to a yield curve.
B/A button
This button changes the price calculation to last bid or ask.
If you choose to build the current curve based upon the last ask or bid prices, then these values are used for those points of the curve where the corresponding contracts are not expired and have dependable quotes with size.
For the other points of the curve, last close prices are used instead.
Mid B/A button
This button changes the price calculation to the midpoint of the last bid or ask.
If you choose to build the current curve based upon these midpoints, then these values are used for those points of the curve where the corresponding contracts are not expired and have dependable quotes with size.
For the other points of the curve, last close prices are used instead.