Hi there, I had the same problem with a knocking sound when i would shake my Macbook 12" back and forth, freaked me out so I took apart my Retina macbook 12" a1354 and found what the problem is. It's a cheap part that can be bought for $9 off ebay called "Display Hinge Clutch Cover". If you look closely in the gap outside in the middle of your macbook 12" you'll see a dark gray/black plastic piece running through the middle of your macbook between the aluminum casing.
+
Hi there, I had the same problem with a knocking sound when i would shake my Macbook 12" back and forth, freaked me out so I took apart my Retina macbook 12" a1354 and found what the problem is. It's a cheap part that can be bought for $9 off ebay called "Display Hinge Clutch Cover". If you look closely in the gap outside in the middle of your macbook 12" you'll see a dark gray/black plastic piece running through the middle of your macbook between the aluminum casing. That's the piece that's causing the trouble. When i had my laptop apart, it was cracked on both side near where it sits inside the laptop hinge. Hope this helps
Hi there, I had the same problem with a knocking sound when i would shake my Macbook 12" back and forth, freaked me out so I took apart my Retina macbook 12" a1354 and found what the problem is. It's a cheap part that can be bought for $9 off ebay called "Display Hinge Clutch Cover". If you look closely in the gap outside in the middle of your macbook 12" you'll see a dark gray/black plastic piece running through the middle of your macbook between the aluminum casing.