 Command entry:
Command entry:Right-click unused area of any toolbar 

 Axis Constraints
            
 The axis constraint buttons and flyouts appear on the Axis Constraints toolbar. See     Using the Axis Constraints.
         
         In Autodesk 3ds Max 2012, while the Axis Constraints toolbar is displayed, its controls update interactively to correspond to the portion of the transform gizmo that you are using currently.
         
          
            Interface
            
  
            NoteThe default UI does not display this toolbar: to see it, right-click an empty portion of any toolbar, and choose Axis Constraints
                  from the menu.
               
              Restrict to X
 Restrict to X
            
 
              Restrict to Y
 Restrict to Y
            
 
              Restrict to Z
 Restrict to Z
            
 
             
               Restrict to Plane flyout
               
 
                 Restrict to XY Plane
 Restrict to XY Plane
               
 
                 Restrict to YZ Plane
 Restrict to YZ Plane
               
 
                 Restrict to ZX Plane
 Restrict to ZX Plane