Before he handles the roll of string, you can tell he's got the threaded pins in his hand, which he holds the entire time, until he slips it into his mouth.

Another thing to notice is how easily the string breaks once he pulls it off the roll. I'll guarantee the string is made of a substance that dissolves in his mouth so he can swallow it. Another indication is the tension on the string used on the threaded needles - if that was the same material as the empty string he eats, it would have broken as he pulled on it.

Had this done to my big toe nail when I was about 13 or 14. Some buddies and I saved up all our monies and rented out an ice rink to play some hockey together. They day before, I was cleaning my room so my parents would let me go. My t.v. was on a rolling stand, and I pulled it out so I could vacuum behind it, but I noticed too late it had three wheels as opposed to the four it was supposed to have. So as I pulled it forward, it tipped over where that missing front wheel was, and slid off the stand. I tried to catch it by the sides, but it was too heavy and slipped through my hands. Quick thinking lad I was, I tried instinctually to catch it with my foot (I didn't want to break my t.v.!), but only managed to catch the very corner of it as it smashed down onto my toe. Luckily my doc used these little threaded needles to make the three holes to relieve the pressure, not the bic and clip method. And indeed it didn't hurt at all, but my step-dad passed out watching them do it. Needless to say the resulting monstrosity didn't fit into an ice skate, and my buddies took my share of the rent and had a good ol' time. A little while later the entire toe nail fell off, and it's never looked the same since.