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3D View » Tool Shelf » Redo panel
Some operations in the 3D View let you adjust their settings after being invoked, so that the operation is actually redone with the new arguments. This is useful to see the results interactively while adjusting the provided parameters. This is accomplished with the generally known as the redo panel (also known as the 'operator panel'), in the bottom part of the Tool Shelf.
This is not actually the official name of the panel, as each operation gives it a specific name. Thus, it can be called Select Random, Add Bezier, Translate, or any other name, depending on the operation.
The initial values of the redo panel are the last used values, or the default values if it is the first time that the operator is used in the current session. The Reset button is used to reset all the panel parameters to their default values.
Every time a redo panel is available, pressing F6 will pop up a window with the same options as the panel.
