When the Lock UI Layout toggle is active, you cannot modify the user interface layout by dragging interface elements. (You can still use the right-click menu to do so, however.) Use this command to prevent user interface changes or inadvertent actions, such as floating toolbars, from happening due to mouse clicks.
To lock the UI layout:
You can no longer move or resize the UI elements. Use this command to prevent user interface changes or if you find yourself accidentally floating toolbars or the command panels on mouse clicks.