Locking an object not only prevents it from being accidentally changed, but it prevents it from even being selected. In a complex illustration, it's often helpful to lock an object so that you can draw or edit around it without accidentally changing it or letting it get in your way.
To lock an object or group of objects
Select the object or group of objects you want to lock.
On the Arrange menu, click Lock (or press CTRL+2).
You can also lock an object or a group of objects in the Layers panel by clicking the padlock icon . When an object is locked, the open padlock changes to a locked padlock .
For more about how to identify and work with objects in the Layers panel, see Layers panel.
The Layers panel displaying one locked layer and one locked object
To unlock an object or group of objects
On the Arrange menu, click Unlock All (or press CTRL+ALT+2).
You can also unlock a single locked object or group from the Layers panel by clicking its locked padlock icon.