I believe he said "you could hammer a nail with it" (00:20). So you're not hammering a nail into the phone, you're using the phone as a hammer to drive the nail

I believe he said "you could hammer a nail with it" (00:20). So you're not hammering a nail into the phone, you're using the phone as a hammer to drive the nail into another surface. It would probably still break if you used the screen as the hammer, but I guess he meant hammering a nail using the side of the phone (which is what you'd normally do anyways).