translate a node on a 2d plane

Maya allows users to easily select and translate (move) objects in the perspective view. Once the object is selected and the transform tool is activated (w), objects can be moved in all three dimensions at once, or on a single axis, depending on whether or not the user left-clicks and drags on the center yellow box (full 3d) or on one of the rbg axis arrows (individual axis).

Maya's standard transform handle; the yellow
box in the center is the free transform manipulator.

Did you know that there is also a way to freely translate an object, but restrict the movement to a specific 2d plane? Let's say, for example, that you wanted to be able to freely move an object on both the X and Z axis, but not the Y. By holding the control key (ctrl) and left-clicking on the axis arrow you want to exclude, the yellow center box of the move tool becomes a plane that describes the other two axis. Now, by left clicking on the center box and dragging the object, you can move freely horizontally, without affecting the vertical position. Try it!

1. Create or select an object
2. Press the W key to activate the move tool
3. CTRL + left click on the colored axis arrow you want to exclude
4. Left-click in the yellow center box and drag the object around, noticing that the exluded axis is not being influenced.
5. To return the manipulator to normal, simply CTRL+ left click on the yellow center plane. It should return to its original box shape.
   

the yellow transform box icon has changed
into a plane, allowing free movement on a
2d plane. CTRL + left-clicking on the icon will
return it the normal free transform cube.

Enjoy!