Because I skipped steps 6, 7, 8, and 11. when removing the hard drive enclosure (I had already the dual drive running, but I needed to replace the drive in the optical enclosure, I found it easier to remove the enclosure by lift the side close to the battery and main HD and pulling it towards myself (towards main HD and battery).

I successfully skipped this step when removing the hard drive enclosure (I had already the dual drive running, but I needed to replace the drive in the optical enclosure. I also skipped steps 6, 7, and 11.

I successfully skipped this step when removing the hard drive enclosure (I had already the dual drive running, but I needed to replace the drive in the optical enclosure. I also skipped steps 7, 8, and 11.

I successfully skipped this step when removing the hard drive enclosure (I had already the dual drive running, but I needed to replace the drive in the optical enclosure. I also skipped steps 6, 8, and 11.