When your selection is locked, you can click or drag the mouse anywhere in the viewports without losing your selection. When you want to deselect or alter your selection, click Selection Lock Toggle again to unlock the selection.
If you want to select something but cannot, it's frequently because you have locked your selection.
This button is off by default.
To turn on 
(Selection Lock Toggle), click the button (it highlights). When Selection Lock Toggle is on, you can click anywhere in a viewport and 3ds Max maintains the current selection. This is useful when you want to keep objects selected while you make a different viewport active or when the selection is tiny, or crowded and difficult to select.
When Maya mode is active, spacebar does not lock the selection. Instead, spacebar activates and maximizes the viewport under the mouse cursor.
Procedures
To transform an object without touching it:
- Use the Selection Floater from the Tools menu,
(Select By Name) on the main toolbar, or press the H key to select the object by name. - On the main toolbar, click a transform button:
(Select And Move), 
(Select And Rotate), or 
(Select And Uniform Scale) on the main toolbar. (You can also choose a different Scale option.) - On the status bar, turn on (Selection Lock Toggle) or press spacebar to lock the selection set.
- Drag anywhere in the viewport.
The object transforms even though you are not touching it.
To avoid accidentally canceling a selection:
-
Make your object selection. - On the status line, click (Selection Lock Toggle), or press spacebar to lock the current selection.
To exit sub-object selection mode, do one of the following:
- In the Modifier Stack display, choose the object level.
- Open another command panel. This turns off Sub-Object selection.
If you've turned off Sub-Object selection and object selection is still not restored, one of the following circumstances might be in effect:
- Your selection is locked. Turn off the Selection Lock toggle on the status line.
- You've set the Selection Filter in the toolbar to a specific category of object, so you can't select any of the other categories. To fix this, choose All in the Selection Filter list.