You can prevent objects on specified layers from being selected and modified by locking those layers.
Typically, you lock layers to prevent accidental editing of particular objects. Other operations are still possible when a layer is locked. For example, you can make a locked layer current, and you can add objects to it. You can also use inquiry commands (such as LIST), use object snaps to specify points on objects on locked layers, and change the draw order of objects on locked layers.
To help you differentiate between locked and unlocked layers, you can do the following: