From BlenderWiki

Manipulators

Description

When using the normal Transform commands (G for Grab, R for Rotation, S for Scale), they will work only parallel to the current view.

Most of the time, though, you need to do axis locking:

• immediately after G, R, or S you can press X, Y or Z to constrain the transform to a global axis
• using MMB will do the same but along the nearest axis from the mouse pointer.

You can do the same using manipulators: they provide a visual representation of the transform and allow movement, rotation and scaling along any axis in any mode and any space (orientation) of the 3D window.

There is a separate manipulator for each Transform Command. Each can be viewed separately or in combination with the others.

Manipulators can be accessed in the header of the 3D View window:

• Hand: Enable/disable the manipulators.
• Triangle: Translation/location.
• Circle: Rotation.
• Box: Scale.
• Transform Orientation menu: choice of the transformation orientation.

Translate.

Rotate.

Scale.

Combination.

Clicking with ⇧ ShiftLMB on the manipulators icons (triangle, circle, box) selects more than one manipulator.
Once manipulators have been enabled, you can quick-select them using CtrlAltG for Grab/Move, CtlrAltR for Rotate, CtrlAltS for Scale.

Manipulator controls

• Holding down Ctrl constrains the action in certain increments (see details here).
• Holding down ⇧ Shift when you LMB click on one of the handles, the manipulator action will be performed on the other two axes to the one you clicked on (you can let go of ⇧ Shift once you have clicked – see also plane axis locking)
• LMB on the white circle (largest circle around rotation manipulator) do the same as pressing R.
• LMB on the grey circle (inner circle around rotation manipulator) do the same as pressing R twice (trackball rotation, see here).

Manipulator Preferences

The settings of the manipulator (e.g. its size) can be found in the View & Controls section of the User Preferences window.

• Size: Diameter of Widget, in 10 pixel units.
• Handle: Size of widget Handles, as a percentage of widget radius (Size/2).
• Hot spot: Hotspot size (in pixels) for clicking Widget Handles.

Choosing Transform Orientation

The default (global) transform manipulator is very useful but in some situations it’s not (for example: scale a rotated object along the rotated axis). Luckily Blender can change the orientation of the Transform Manipulator.

For more precisions about the transform orientations, see this page.