This is for mounting your iPhone4 on a tripod. Charging of the iPhone is possible while being connected to the tripod. You can also stand your iPhone in different ways.
Mounting your iPhone to a tripod can make a big difference when trying to make a watchable movie.
Buy a 1/4 inch nut, and screw it into the large hole on the bottom. Tip: Heating the nut makes it easier, without damaging the print. Make sure the plastic holds your iPhone tight before giving gravity a shot at taking it away.