Lock
            a paint layer to avoid accidentally modifying the image on that
            layer. The image on that layer remains visible but cannot be edited
            when it is locked.
         
         
            - In the Layers window,
               click the space in the lock column beside the layer you want to
               lock.
               A lock icon appears to
                  indicate the layer is locked.
                
- Click the lock icon a second time to
               unlock the layer.