Set Object Axis
Default Shortcut: None
Menu Path: Selection > Set Object Axis
The Set Object Axis command can be used to assign the currently selected object's axis to wherever the manipulator is currently. You can use this to place the object's pivot point (which is normally at the center of the object) wherever you like. A common example is rotating an object about an edge. Select the edge, use Set Object Axis, switch to object mode (see Selection Mode), and rotate the object.